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ABSTRACT

The present invention relates to a diecut especially for the permanent closing of holes especially in metal sheets or in plastics parts, having a carrier composed of an assembly, more particularly laminate in the specified layer sequence, of optionally at least one first layer, which is formed by a metallic layer having a thickness of 10 to 40 μm, optionally at least one second layer, which is formed by a woven glass fabric or laid glass fabric having a basis weight of 30 to 200 g/m2, optionally at least one third layer, which is formed by a first pressure-sensitive adhesive having a basis weight of 70 to 200 g/m2, at least one fourth layer, which is formed by a flame-retardant foam having a thickness of at least 0.5 to 2.5 mm, and at least one fifth layer, which is formed by a second, acrylate-based pressure-sensitive adhesive having a basis weight of 300 to 1800 g/m2, preferably 360 to 1500 g/m2 and/or a thickness of 400 to 1800 μm, preferably 800 to 1500 μm.

This is an application claims priority to DE 02020209289.3 filed 23.Jul. 2020. The present application claims the full priority benefit ofthis prior application and herein incorporates its entirety.

The present invention relates to a diecut especially for the permanentclosing of holes which are located preferably in metal sheets or inplastics parts of, in particular, vehicles, and also to a method forpermanently closing holes.

In the fabrication of relatively complex structures from metal sheetsand/or plastics, constructional dictates make it impossible to avoidhaving to cut holes in the sheets or plastics, in order to gain accessto cavities situated behind them, whether for the purpose of painting orfor the purpose of welding.

When the desired operation has been concluded, these holes are usuallyno longer needed, and are often in fact disruptive, since they allow thepassage of air, atmospheric moisture or water into the structure, whichmay lead, for example, to processes of oxidation (rust).

One simple solution to avoiding these problems is to close the holesagain after use.

Particularly in the production of modern vehicles such as watercraft,land vehicles (trucks, automobiles, etc.), air vehicles, space vehicles,and combinations thereof, such as amphibious vehicles, for example, itis inevitable that during assembly, in numerous individual parts madefrom metal sheets or plastics, holes of different sizes are required.The hole diameters are typically between 5 and 50 mm. In subsequentoperation, many of these holes must be given airtight and in particularwatertight closure again, in order to prevent said corrosive attacks.Another requirement is to achieve a considerable improvement in thesound proofing of the passenger interior through the closing of theholes.

The problems underlying the invention, and also the solution to theseproblems, are described below using the body of a car as an example.This expressly does not restrict the concept of the invention to thisutility. This utility is part of the technical field in which theinvention is manifested to particular advantage.

If from this point on there is reference to use in a vehicle body, theskilled person reads this as embracing all other possible utilities aswell as a vehicle body.

In automotive construction, holes must be made, or punched out, atvarious locations in the vehicle body. Generally this is done as part ofthe operation of punching and forming the individual sheet-metal oraluminum parts; additionally, holes may also be drilled in plasticscomponents. Subsequently, by means of a variety of joining processes,the individual metal parts are connected with one another, and thebodyshell is formed. The uses of the holes, openings or passages in thisbodyshell include their use as paint drainage holes (for cathodicelectrocoat materials, for example), wax injection holes, wax drainageholes, holes for later screw-mounting operations in assembly, or forcable passages. After the cathodic electrocoat material has dried, manyof these holes must be closed again, or else must be closed after thefinal clearcoat operation (in which case hole closure would take placein the assembly process).

There are many possible reasons why a hole needs to be closed, examplesbeing:

-   -   moisture    -   acoustics    -   corrosion prevention.

Generally speaking, the holes or openings are closed usinginjection-molded parts (plugs) made from different plastics manufacturedaccording to the profile of requirements. These may be, for example,plugs made from PET, ABS, PP, PVC, EPDM, PA and further commercialplastics, or else combinations of the stated materials and customarycommercial polymeric substrates not listed here. Also in use arematerials which possess a glass fiber fraction; also conceivable arecarbon fibers, which strengthen the plug against being pushed through,for example. In principle all common polymeric substrates are possible,provided that they offer particular parameters in relation topaintability, temperature stability, dimensional stability underclimatic conditions, and also fulfill a certain economy in the plugmanufacturing process.

At the present time, vehicle bodywork holes are generally closed usingplastic plugs which on the one hand, in a particular scenario, do notsecurely close the hole, and on the other hand are comparativelycomplicated and expensive to produce.

Each size of hole requires a specific plug adapted to the hole size.This entails high logistical and administrative effort for the consumerof the plugs.

On the production line it is necessary accordingly to hold a largenumber of plugs of different sizes in individually assigned storagecrates.

Also suitable for this purpose are adhesive tapes, which are cut tolength or die-cut in accordance with the hole size. Adhesive tapes aswell, however, do not always meet the increasingly high requirements ofthe market.

The intention here is to look more closely at the self-adhesive holeclosures which are required to achieve an acoustic effect.

These acoustically relevant hole closures are often used in assembly inorder to obtain an isolated region, the vehicle interior, within thepassenger cell. Disruptive acoustics in the vehicle interior aregenerated, for example, by rolling noises from the tires or else byloose gravel and also small chippings which are thrown against thevehicle paneling and also against the vehicle's structural members.Moreover, wind noises which come about as a result of unstreamlineddesign are another possible cause of a relatively high, unwanted noiselevel within the passenger cell.

The noise caused by loose gravel, chippings, rolling noises from thetires, and by unevenesses in the ground is often transmitted into thecavities in the structural member systems (side and crossmembers) andinto the vehicle interior or passenger cell. As a result of this,products with acoustic activity must also be employed outside thevehicle. One form of effective acoustic protection, for example, is totape off holes in the floor assembly and/or in the vehicle platform.Holes, punched apertures or drilled apertures are often made in the sideand crossmembers. Here, particular attention must be paid to carefullyclosing every possible opening.

As already described, numerous holes in the sheet-metal bodywork parts,or in the structural member systems, serve to allow the cathodicelectrocoat material to drain as rapidly as possible from the body andfrom all kinds of cavities, in order to secure operating time. Thismeans, conversely, that the openings and holes must be reliably closedimmediately downstream of the cathodic electrocoat drier. Generally thisis done on what is called the PVC line. This area involves amanufacturing step which takes place before application ofprimer-surfacer or before application of basecoat material. A furtherfeature to be fulfilled, therefore, is that of repaintability forproducts which are employed within this production segment. Moreover,there must be compatibility with PVC seam-sealing material, since gapsare sealed with pumpable PVC compounds between the cathodic electrocoatdrier and the next coating layer.

Hole closure products based on heavy-duty film in combination with afilm applied to the top side are known from EP 3 036 100 A1. Disclosedtherein is a diecut especially for the permanent closing of holes,particularly in metal sheets or in plastics parts, having a carriercomprising a laminate of at least two polymeric films, the lower filmhaving a basis weight of at least 1.5 kg/m², more particularly between1.5 and 6 kg/m², and the side of the lower film opposite the upper filmbearing an applied adhesive, more particularly a curable orself-adhesive composition. The upper film consists preferably ofpolyester, more preferably of polyethylene terephthalate (PET).

Besides the conventional vehicles with internal combustion engines,hybrid electric-powered vehicles (HEV for Hybrid Electric Vehicle) andelectric automobiles with batteries (BEV for Battery Electric Vehicle)are increasingly gaining importance.

A hybrid electric vehicle is a vehicle with a hybrid drive, in otherwords an electric vehicle which is driven by at least one electric motorand also by a further energy convertor, and which draws energy both fromits electrical accumulator (battery) and from a fuel carriedadditionally. A fully electric vehicle is driven exclusively by abattery-operated electric motor and therefore requires no fossil fuel.The battery is charged via external network components.

A problem with these vehicles is the batteries located in the body, suchas lithium-ion batteries. A burning lithium-ion battery is much moredifficult to extinguish than a burning petrol or diesel vehicle.

Consequently there is also a continual increase in the safetyrequirements governing batteries in electric automobiles. The OEMs areattempting with maximum assurance to respond to the requirements bypreventing the spread of fire from the battery compartment into thevehicle through, for example, the holes in the bodywork. Because therequirements with regard to flame temperatures and also to time topenetration are not precisely stipulated, the solutions employed areprimarily those which cover maximum possible temperature ranges and timespans.

Initial products are available with the capacity to meet the exactingrequirements imposed. Tesa® 54332 from tesa SE combines an extremelyheat-resistant carrier composed of aluminum and woven glass fiber fabricwith an extra-thick acrylate adhesive. The product is optimized forutilities in car making, in order to close unused bodywork apertures,where excellent heat resistance and flawless sealing are required. Thisproduct withstands a horizontal fire test at temperatures up to 500° C.for at least 5 minutes. The test determines the time to penetration ofthe flame at the respective temperature. The construction and theimplementation of the fire test are described in detail later on below.

GTR 20 (Global Technical Regulation No. 20) in the version of 3 May 2018lays down the requirements currently imposed on BEVs in respect, forexample, of fire protection in the battery packs. The OEMs/OESs areattempting to provide maximum fire resistance to surrounding componentsas well (for example diecut parts in the underbody).

It is an object of the invention to provide a diecut which is suitablefor permanently closing holes, especially in metal sheets or in plasticsparts of car bodies, and which closes said holes such that moisturepenetration is impossible, which can be repainted with at least some ofthe customary paints, which enhances soundproofing and provides reliablesealing with respect to mechanical exposures in the interior,particularly in the floor area, and which offers an improvement in theresistance to heat and fire.

This object is achieved by means of a diecut as specified in the mainclaim. The dependent claims provide advantageous onward developments ofthe subject matter of the invention.

FIG. 1 illustrates an embodiment of a diecut of the invention, locatedwith respect to a hole in a body that is to be closed, and also thestate after closure of the hole that was to be closed.

FIG. 2 depicts a graph which may be used in evaluation of glasstransition temperature.

FIGS. 3a and 3b illustrate the arrangement of elements use in a verticalfire test (FIG. 3a ) and in a horizontal fire test (FIG. 3b ).

The invention accordingly provides a diecut especially for the permanentclosing of holes especially in metal sheets or in plastics parts, havinga carrier composed of an assembly, more particularly laminate in thespecified layer sequence, of optionally at least one first layer, whichis formed by a metallic layer having a thickness of 10 to 40 μm,optionally at least one second layer, which is formed by a woven glassfabric or laid glass fabric having a basis weight of 30 to 200 g/m²,optionally at least one third layer, which is formed by a firstpressure-sensitive adhesive having a basis weight of 70 to 200 g/m², atleast one fourth layer, which is formed by a flame-retardant foam havinga thickness of 0.5 to 2.5 mm, and at least one fifth layer, which isformed by a second pressure-sensitive adhesive having a basis weight of300 to 1800 g/m², preferably 360 to 1500 g/m² and/or a thickness of 400to 1800 μm, preferably 800 to 1500 μm.

A preferred embodiment of the diecut is that wherein at least the first,second, third, fourth and fifth layers are present simultaneously.

According to one advantageous embodiment of the invention, the firstmetallic layer has a thickness of 12 to 20 μm, more preferably 18 μm. Itmay also feature embossing.

Metals selectable include silver, copper, gold, platinum, aluminum andaluminum compounds, tin, nichrome, Nirosta, titanium, and metal oxidessuch as cadmium oxides, tin oxides, zinc oxides and magnesium oxides.Selected with particular preference is aluminum. This recitation shouldnot be considered here to be exhaustive; instead, the skilled person isable to select further metal layers, not explicitly stated here, withoutdeparting from the concept of the invention.

The metallic layer preferably comprises a rolled metal foil, moreparticularly aluminum foil.

With further advantage, in accordance with the invention, the firstmetallic layer used may comprise layers of metal oxide (MeOx layers).Advantageous metal oxide layers consist, for example, of silicon dioxide(SiO₂), titanium dioxide (TiO₂) or zinc tin oxide (ZnSnO), or compriseone or more of these metal oxides.

The woven or laid glass fabric of the second layer advantageously hasproperties as follows: The basis weight is between 60 and 120 g/m², moreparticularly between 70 and 100 g/m², further in particular between 80and 90 g/m².

The warp thread count and/or the weft thread count are/is in each case 3to 50 threads/cm. According to another advantageous embodiment of theinvention, the warp thread count is 5 to 10/cm, preferably 7/cm and/orthe weft thread count is 4 to 10/cm, preferably 5/cm.

The thread weight of the longitudinal and transverse threads ispreferably between 500 and 1000 dtex, more preferably between 600 and800 dtex, with particular preference 680 dtex.

The transverse titer is the term used for the number of transversethreads (weft threads) per centimeter, multiplied by the thread weightof the transverse threads in dtex. The unit is dtex/cm.

The longitudinal titer is the term used for the number of longitudinalthreads (warp threads) per centimeter, multiplied by the thread weightof the longitudinal threads in dtex. The unit is again dtex/cm.

According to another advantageous embodiment of the invention, thelongitudinal titer of the longitudinal threads and/or the transversetiter of the transverse threads is greater than 2000 dtex/cm. Withpreference the longitudinal titer is between 4000 and 5000 dtex/cmand/or the transverse titer is between 3000 and 4000 dtex/cm.

In a woven glass fabric, the threads are woven in a plain weave. Othertypes of weave are sateen (also known as satin, of which there areregular and irregular forms) and twill. A twill weave (for example a “2over 1 twill”) generates what is called a twill line, which runsdiagonally to the machine direction.

A laid fabric is a sheetlike structure consisting of one or more pliesof stretched threads running in parallel. The threads are typicallyfixed at the points where they cross. Fixing is accomplished either bycohesive bonding or mechanically by friction and/or interlocking.

The following types of laid-filament fabrics are in existence:

-   -   monoaxial or unidirectional fabrics, formed by the fixing of one        group of parallel threads biaxial fabrics, in which two groups        of parallel threads are fixed in the direction of two axes    -   multiaxial fabrics: a plurality of groups of parallel threads        are fixed in the direction of different axes.

The plies of threads in the case of multi-ply laid fabrics may all havedifferent orientations, and may also consist of different threaddensities, including different linear densities.

Preferred in the invention are single-ply laid fabrics.

Between the first metallic layer and the second layer in the form of awoven or laid glass fabric there may be functional layers such as, forinstance, adhesion promoters for improving the composite adhesion.Preference is given to using a further adhesive layer in the form of alaminating adhesive, specifically having a unit area coat weight of 5 to50 g/m², more particularly of 7 to 20 g/m².

Suitable laminating adhesives include, in particular, pressure-sensitiveadhesives, as elucidated comprehensively below.

An alternative possibility is for the first metallic layer and thesecond layer in the form of a woven or laid glass fabric to be joinedtogether by lamination under pressure.

For the third layer, which is formed by a first pressure-sensitiveadhesive having a basis weight of 70 to 200 g/m², all known adhesivesystems may be employed. As well as adhesives based on natural orsynthetic rubber, silicone adhesives and also polyacrylate adhesives inparticular may be used.

The adhesive is preferably a pressure-sensitive adhesive (PSA), thisbeing an adhesive which even under relatively weak applied pressurepermits a durable bond to virtually all substrates and which after usecan be detached from the substrate again substantially without residue.A pressure-sensitive adhesive is permanently tacky at room temperature,thus having a sufficiently low viscosity and a high initial tack, sothat it wets the surface of the respective substrate even at low appliedpressure. The bondability of the adhesive derives from its adhesiveproperties, and the redetachability from its cohesive properties.

PSAs may be regarded as liquids of extremely high viscosity with anelastic component. Accordingly they have particular, characteristicviscoelastic properties which result in the permanent inherent tack andadhesiveness.

A characteristic of PSAs is that when they are mechanically deformed,there are processes of viscous flow and there is also development ofelastic forces of resilience. The two processes have a certainrelationship to one another in terms of their respective proportion, independence not only on the precise composition, the structure and thedegree of crosslinking of the respective PSA but also on the rate andduration of the deformation, and on the temperature.

The proportional viscous flow is necessary for the achievement ofadhesion. Only the viscous components, brought about by macromoleculeswith relatively high mobility, permit effective wetting and effectiveflow onto the substrate to be bonded. A high viscous flow componentresults in high pressure-sensitive adhesiveness (also referred to astack or surface tackiness) and hence often also in a high peel adhesion.Owing to a lack of flowable components, generally speaking, highlycrosslinked systems and polymers which are crystalline or have undergoneglasslike solidification have at least only a little tack, or none atall.

The proportional elastic forces of resilience are necessary for theattainment of cohesion. They are brought about, for example, by verylong-chain macromolecules with a high degree of coiling, and also byphysically or chemically crosslinked macromolecules, and they allow thetransmission of the forces that act on an adhesive bond. As a result ofthese forces of resilience, an adhesive bond is able to withstand along-term load acting on it, in the form of a long-term shearing load,for example, sufficiently over a relatively long period.

It is possible here to employ all known adhesive systems. Besidesnatural or synthetic rubber-based adhesives there are, in particular,silicone adhesives and also polyacrylate adhesives, preferably a lowmolecular mass acrylate hotmelt pressure-sensitive adhesive, that can beused.

Preferred adhesives are those based on acrylate or silicone.

The adhesive may be selected from the group of the natural rubbers orthe synthetic rubbers, or from any desired blend of natural rubbersand/or synthetic rubbers, with the natural rubber or rubbers beingselectable in principle from all available grades such as, for example,crepe, RSS, ADS, TSR or CV products, depending on the required level ofpurity and of viscosity, and the synthetic rubber or rubbers beingselectable from the group of the randomly copolymerizedstyrene-butadiene rubbers (SBR), butadiene rubbers (BR), syntheticpolyisoprenes (IR), butyl rubbers (IIR), halogenated butyl rubbers(XIIR), acrylate rubbers (ACM), ethylene-vinyl acetate copolymers (EVA)and polyurethanes and/or blends thereof.

Likewise preferably the adhesive coating consists of an adhesive basedon synthetic rubber, more particularly an adhesive composed of at leastone vinyl aromatic block copolymer and at least one tackifier resin.Typical concentrations for use of the block copolymer lie at aconcentration in the range between 30 wt % and 70 wt %, moreparticularly in the range between 35 wt % and 55 wt %.

Further polymers present may be those based on pure hydrocarbon atomssuch as, for example, unsaturated polydienes such as natural orsynthetically generated polyisoprene or polybutadiene, chemicallysubstantially saturated elastomers such as, for example, saturatedethylene-propylene copolymers, -olefin copolymers, polyisobutylene,butyl rubber, ethylene-propylene rubber, and also chemicallyfunctionalized hydrocarbon atoms such as, for example,halogen-containing, acrylate-containing or vinyl ether-containingpolyolefins, which may replace up to half of the vinylaromatic-containing block copolymers.

Serving as tackifiers are tackifier resins which are compatible with theelastomer block of the styrene block copolymers.

Plasticizing agents such as, for example, liquid resins, plasticizeroils or low molecular mass liquid polymers such as, for example, lowmolecular mass polyisobutylenes having molar masses<1500 g/mol (numberaverage) or liquid EPDM products are typically employed.

Further additives possibly added to all stated types of adhesivesinclude light stabilizers such as, for example, UV absorbers, stericallyhindered amines, antiozonants, metal deactivators, processing aids,endblock-reinforcing resins.

Fillers such as, for example, silicon dioxide, glass (ground or in theform of beads, as solid or hollow beads), microballoons, aluminumoxides, zinc oxides, calcium carbonates, titanium dioxides, carbonblacks, silicates and chalk, to name but a few, and also color pigmentsand dyes, and optical brighteners as well, may likewise be used.

PSAs are typically admixed with primary and secondary antioxidants inorder to improve their aging stability. Primary antioxidants react withoxy and peroxy radicals, which can form in the presence of oxygen, andreact with them to form less reactive compounds. Secondary antioxidantsreduce hydroperoxides to alcohols, for example. There is known to be asynergistic effect between primary and secondary aging inhibitors, andso the protective effect of a mixture is frequently greater than the sumof the two individual effects.

With further preference the rubbers may have their processing qualitiesenhanced by admixing of thermoplastic elastomers with a weight fractionof 10 to 50 wt %, this figure being based on the overall elastomerfraction.

Representatives that may be mentioned at this point include inparticular the especially compatible styrene-isoprene-styrene (SIS) andstyrene-butadiene-styrene (SBS) products. Suitable elastomers forblending are also, for example, EPDM or EPM rubber, polyisobutylene,butyl rubber, ethylene-vinyl acetate, hydrogenated block copolymers madefrom dienes (for example by hydrogenation of SBR, cSBR, BAN, NBR, SBS,SIS or IR; such polymers are known in the form of SEPS and SEBS, forexample), or acrylate copolymers such as ACM. In addition a 100% systembased on styrene-isoprene-styrene (SIS) has been found to be suitable.

Crosslinking is advantageous for improving the removability of theadhesive tape after use, and may be accomplished thermally or byirradiation with UV light or electron beams. For the purpose of thethermally induced chemical crosslinking it is possible to use all known,thermally activatable chemical crosslinkers such as accelerated sulfuror sulfur donor systems, isocyanate systems, reactive melamine,formaldehyde and (optionally halogenated) phenol-formaldehyde resinsand/or reactive phenolic resin or diisocyanate crosslinking systems withthe corresponding activators, epoxidized polyester resins and acrylateresins, and also combinations of these.

The crosslinkers are activated preferably at temperatures above 50° C.,more particularly at temperatures of 100° C. to 160° C., very preferablyat temperatures of 110° C. to 140° C.

The thermal excitation of the crosslinkers may also be accomplished bymeans of IR rays or high-energy alternating fields.

Solvent-based or aqueously-based adhesives may be used, or elseadhesives in the form of a hotmelt system. An acrylate hotmelt-basedadhesive is suitable as well, and may have a K value of at least 20,more particularly greater than 30, obtainable by concentrating asolution of such an adhesive to form a system which can be processed asa hotmelt.

Concentration may take place in appropriately equipped tanks orextruders; especially in the case of accompanying degassing, adevolatilizing extruder is preferred.

One adhesive of this kind is set out in DE 43 13 008 A1, the content ofwhich is hereby referenced and made part of the present disclosure andinvention.

The acrylate hotmelt-based adhesive may also be chemically crosslinked,however.

The K value here is determined in particular in analogy to DIN 53 726.

In addition, further volatile constituents are removed in the process.After having been coated from the melt, these compositions retain onlysmall fractions of volatile constituents. It is therefore possible toadopt all of the monomers/formulas claimed in the patent indicatedabove.

The solution of the composition may have a solvent content of 5 to 80 wt%, more particularly 30 to 70 wt %.

Commercial solvents are preferably used, being, in particular,low-boiling hydrocarbon atoms, ketones, alcohols and/or esters.

Further preference is given to using single-screw, twin-screw ormulti-screw extruders with one or more particularly with two or moreventing units.

The acrylate hotmelt-based adhesive may have benzoin derivativescopolymerized in it, as for example benzoin acrylate or benzoinmethacrylate, acrylic or methacrylic esters. Such benzoin derivativesare described in EP 0 578 151 A.

The acrylate hotmelt-based adhesive may be UV-crosslinked. Other formsof crosslinking are also possible though, with electron beamcrosslinking being an example.

In a further preferred embodiment, self-adhesive compositions used arecopolymers of (meth)acrylic acid and esters thereof having 1 to 25carbon atoms, maleic, fumaric and/or itaconic acid and/or their esters,substituted (meth)acrylamides, maleic anhydride and other vinylcompounds, such as vinyl esters, especially vinyl acetate, vinylalcohols and/or vinyl ethers.

One adhesive which has likewise shown itself to be suitable is a lowmolecular mass acrylate hotmelt pressure-sensitive adhesive, as carriedby BASF under the designation acResin UV or Acronal®, more particularlyAcronal® DS 3458 or AC Resin A 260UV. This low K value adhesive acquiresits application-matched properties by virtue of a concludingcrosslinking procedure initiated chemically by radiation.

Other outstandingly suitable adhesives are described in EP 2 520 627 A1,EP 2 522 705 A1, EP 2 520 628 A1, EP 2 695 926 A1 and EP 2 520 629 A1.

Particularly preferred is a PSA in the form of a dried polymerdispersion, the polymer being composed of:

-   -   (a) 95.0 to 100.0 wt % of n-butyl acrylate and/or 2-ethylhexyl        acrylate    -   (b) 0.0 to 5.0 wt % of an ethylenically unsaturated monomer        having an acid or acid anhydride function.

The polymer consists preferably of 95.0 to 99.5 wt % of n-butyl acrylateand/or 2-ethylhexyl acrylate and 0.5 to 5 wt % of an ethylenicallyunsaturated monomer having an acid or acid anhydride function, morepreferably of 97.0 or 98.0 wt % to 99.0 wt % of n-butyl acrylate and/or2-ethylhexyl acrylate and 1.0 to 2.0 wt % or 3 wt % of an ethylenicallyunsaturated monomer having an acid or acid anhydride function.

Besides the acrylate polymers recited, and besides any residual monomerspresent, the PSA may additionally be admixed with tackifiers and/oradjuvants such as light stabilizers or aging inhibitors. In particularthere are no further polymers such as elastomers present in the PSA,meaning that the polymers of the PSA consist only of the monomers (a)and (b) in the proportions indicated.

Monomer (a) is preferably formed by n-butyl acrylate.

Examples of monomers contemplated as (b) advantageously include acrylicacid, methacrylic acid, itaconic acid, maleic acid, fumaric acid and/ormaleic anhydride.

Preferred is (meth)acrylic acid of the formula I,

where R³ is ═H or CH₃; preference is given optionally to using themixture of acrylic acid or methacrylic acid. Acrylic acid isparticularly preferred.

According to one particularly preferred variant, the composition of thepolymer is as follows:

-   -   (a) 95.0 to 100.0 wt %, preferably 95.0 to 99.5 wt %, more        preferably 98.0 to 99.0 wt % of n-butyl acrylate and    -   (b) 0.0 to 5.0 wt %, preferably 0.5 to 5.0 wt %, more preferably        1.0 to 2.0 wt % of acrylic acid.

The polymer dispersion is prepared by the process of emulsionpolymerization of the stated components. Descriptions of this processcan be found for example in “Emulsion Polymerization and EmulsionPolymers” by Peter A. Lovell and Mohamed S. El-Aasser—Wiley-VCH1997—ISBN 0-471-96746-7 or in EP 1 378 527 B1.

During the polymerization it is not impossible for not all of themonomers to undergo reaction to form polymers. It is obvious here thatthe residual monomer content is to be as small as possible. Preferenceis given to providing adhesives comprising the polymer dispersion with aresidual monomer content of less than or equal to 1 wt %, moreparticularly less than or equal to 0.5 wt % (based on the mass of thedried polymer dispersion).

Lastly it may be mentioned that polyurethane-based adhesives are alsosuitable.

To optimize the properties it is possible for the self-adhesivecomposition employed to have been blended with one or more additivessuch as tackifiers (resins), plasticizers, fillers, pigments, UVabsorbers, light stabilizers, aging inhibitors, crosslinking agents,crosslinking promoters or elastomers.

Tackifiers used are those resins already comprehensively described.

Examples of suitable fillers and pigments are carbon black, titaniumdioxide, calcium carbonate, zinc carbonate, zinc oxide, silicates orsilica.

Suitable plasticizers are, for example, aliphatic, cycloaliphatic andaromatic mineral oils, diesters or polyesters of phthalic acid,trimellitic acid or adipic acid, liquid rubbers (for example nitrilerubbers or polyisoprene rubbers), liquid polymers of butene and/orisobutene, acrylic esters, polyvinyl ethers, liquid resins andplasticizing resins based on the raw materials for tackifier resins,wool wax and other waxes, or liquid silicones.

Crosslinking agents are, for example, phenolic resins or halogenatedphenolic resins, melamine and formaldehyde resins. Suitable crosslinkingpromoters are, for example, maleimides, allyl esters such as triallylcyanurate, and polyfunctional esters of acrylic and methacrylic acid.

A “tackifier resin” is, in accordance with the general understanding ofthe skilled person, an oligomeric or polymeric resin which raises theautoadhesion (the tack, the inherent stickiness) of the PSA bycomparison with the otherwise identical PSA containing no tackifierresin.

The use of tackifiers for boosting the peel adhesion values of PSAs isknown fundamentally. This effect also comes about if the adhesive isadmixed with up to 15 parts by weight (corresponding to <15 parts byweight), or 5 to 15 parts by weight, of tackifiers (based on the mass ofthe dried polymer dispersion). Preference is given to adding 5 to 12,more preferably 6 to 10 parts by weight of tackifiers (based on the massof the dried polymer dispersion).

Suitable tackifiers, also referred to as tackifier resins, are inprinciple all known classes of compound. Tackifiers are, for example,hydrocarbon resins (for example polymers based on unsaturated C₅ or C₉monomers), terpene-phenolic resins, polyterpene resins based on rawmaterials such as, for example, — or R-pinene, aromatic resins such ascoumarone-indene resins or resins based on styrene or -methylstyrenesuch as rosin and its derivatives, examples being disproportionated,dimerized or esterified rosin, as for example reaction products withglycol, glycerol or pentaerythritol, to name but some. Preferred resinsare those without readily oxidizable double bonds such asterpene-phenolic resins, aromatic resins and more preferably resinsprepared by hydrogenation such as, for example, hydrogenated aromaticresins, hydrogenated polycyclopentadiene resins, hydrogenated rosinderivatives or hydrogenated polyterpene resins. Preferred resins arethose based on terpene phenols and rosin esters. Likewise preferred aretackifier resins having an ASTM E28-99 (2009) softening point of morethan 80° C. Particularly preferred resins are those based on terpenephenols and rosin esters having an ASTM E28-99 (2009) softening point ofmore than 90° C. The resins are used advantageously in dispersion form.In that form they can readily be subjected to finely divided mixing withthe polymer dispersion.

In a particularly preferred variant no tackifier resins at all have beenadded to the PSA.

Not added to the PSA in particular are the following substances:

-   -   hydrocarbon resins (for example polymers based on unsaturated C₅        or C₉ monomers) terpene-phenolic resins    -   polyterpene resins based on raw materials such as — or β-pinene,        for example aromatic resins such as coumarone-indene resins or        resins based on styrene or        -   methylstyrene such as rosin and its derivatives, as for            example disproportionated, dimerized or esterified rosin,            examples being reaction products with glycol, glycerol or            pentaerythritol.

A “poly(meth)acrylate” is a polymer of which at least 60 wt % of itsmonomer basis consists of acrylic acid, methacrylic acid, acrylic estersand/or methacrylic esters, with acrylic esters and/or methacrylic estersbeing included at least proportionally, preferably at not less than 50wt %, based on the overall monomer basis of the polymer in question.More particularly a “poly(meth)acrylate” is a polymer which isobtainable by radical polymerization of acrylic and/or methacrylicmonomers and also, optionally, further, copolymerizable monomers.

In the invention the poly(meth)acrylate or poly(meth)acrylates is or arepresent at 30 to 65 wt %, based on the total weight of the PSA. The PSAof the invention comprises preferably 35 to 55 wt % of at least onepoly(meth)acrylate, based on the total weight of the PSA.

The glass transition temperature of the poly(meth)acrylates which can beused in the invention is preferably <0° C., more preferably between −20and −50° C.

The glass transition temperature of polymers or of polymer blocks inblock copolymers is determined for the purposes of this invention bydynamic scanning calorimetry (DSC).

The poly(meth)acrylates of the PSA of the invention are obtainablepreferably by at least proportional copolymerization of functionalmonomers which preferably are crosslinkable with epoxide groups. Thesemonomers are more preferably those with acid groups (particularlycarboxylic, sulfonic or phosphonic acid groups) and/or hydroxyl groupsand/or acid anhydride groups and/or epoxide groups and/or amine groups;especially preferred are monomers containing carboxylic acid groups. Itis particularly advantageous for the polyacrylate to containcopolymerized acrylic acid and/or methacrylic acid. All of these groupsfeature crosslinkability with epoxide groups, thereby making thepolyacrylate amenable advantageously to thermal crosslinking withintroduced epoxides.

Other monomers which may be used as comonomers for thepoly(meth)acrylates, aside from acrylic and methacrylic esters having upto 30 carbon atoms per molecule, are, for example, vinyl esters ofcarboxylic acids containing up to 20 carbon atoms, vinyl aromaticshaving up to 20 carbon atoms, ethylenically unsaturated nitriles, vinylhalides, vinyl ethers of alcohols containing 1 to 10 carbon atoms,aliphatic hydrocarbon atoms having 2 to 8 carbon atoms and one or twodouble bonds, or mixtures of these monomers.

The properties of the poly(meth)acrylate in question may be influencedin particular by variation in the glass transition temperature of thepolymer through different weight fractions of the individual monomers.The poly(meth)acrylate(s) of the invention may derive preferably fromthe following monomer composition:

a) acrylic esters and/or methacrylic esters of the following formula

CH₂═C(R′)(COOR″)

-   -   where R′ is ═H or CH₃ and R″ is an alkyl radical having 4 to 14        carbon atoms,

b) olefinically unsaturated monomers having functional groups of thekind already defined for reactivity with epoxide groups,

c) optionally further acrylates and/or methacrylates and/or olefinicallyunsaturated monomers which are copolymerizable with component (a).

The fractions of the corresponding components (a), (b) and (c) arepreferably selected such that the polymerization product has a glasstransition temperature of <0° C., more preferably between −20 and −50°C. (DSC). It is particularly advantageous to select the monomers ofcomponent (a) with a fraction of 45 to 99 wt %, the monomers ofcomponent (b) with a fraction of 1 to 15 wt % and the monomers ofcomponent (c) with a fraction of 0 to 40 wt % (the figures are based onthe monomer mixture for the “basic polymer”, in other words withoutadditions of any additives to the completed polymer, such as resins,etc.).

The monomers of component (a) are more particularly plasticizing and/ornon-polar monomers. Used preferably as monomers (a) are acrylic andmethacrylic esters having alkyl groups consisting of 4 to 14 carbonatoms, more preferably 4 to 9 carbon atoms. Examples of such monomersare n-butyl acrylate, n-butyl methacrylate, n-pentyl acrylate, n-pentylmethacrylate, n-amyl acrylate, n-hexyl acrylate, n-hexyl methacrylate,n-heptyl acrylate, n-octyl acrylate, n-octyl methacrylate, n-nonylacrylate and their branched isomers, such as, for example, isobutylacrylate, isooctyl acrylate, isooctyl methacrylate, 2-ethylhexylacrylate or 2-ethylhexyl methacrylate.

The monomers of component (b) are more particularly olefinicallyunsaturated monomers having functional groups, especially havingfunctional groups able to enter into a reaction with epoxide groups.

Used preferably for component (b) are monomers having functional groupsselected from the group encompassing the following: hydroxyl, carboxyl,sulfonic acid or phosphonic acid groups, acid anhydrides, epoxides,amines.

Particularly preferred examples of monomers of component (b) are acrylicacid, methacrylic acid, itaconic acid, maleic acid, fumaric acid,crotonic acid, aconitic acid, dimethylacrylic acid,β-acryloyloxypropionic acid, trichloroacrylic acid, vinyl acetic acid,vinyl phosphonic acid, maleic anhydride, hydroxyethyl acrylate,especially 2-hydroxyethyl acrylate, hydroxypropyl acrylate, especially3-hydroxypropyl acrylate, hydroxybutyl acrylate, especially4-hydroxybutyl acrylate, hydroxyhexyl acrylate, especially6-hydroxyhexyl acrylate, hydroxyethyl methacrylate, especially2-hydroxyethyl methacrylate, hydroxypropyl methacrylate, especially3-hydroxypropyl methacrylate, hydroxybutyl methacrylate, especially4-hydroxybutyl methacrylate, hydroxyhexyl methacrylate, especially6-hydroxyhexyl methacrylate, allyl alcohol, glycidyl acrylate, glycidylmethacrylate.

In principle it is possible as component (c) to use all vinylicallyfunctionalized compounds which are copolymerizable with component (a)and/or with component (b). The monomers of component (c) may serve toadjust the properties of the resultant PSA.

Illustrative monomers of component (c) are as follows:

methyl acrylate, ethyl acrylate, propyl acrylate, methyl methacrylate,ethyl methacrylate, benzyl acrylate, benzyl methacrylate, sec-butylacrylate, tert-butyl acrylate, phenyl acrylate, phenyl methacrylate,isobornyl acrylate, isobornyl methacrylate, tert-butylphenyl acrylate,tert-butylphenyl methacrylate, dodecyl methacrylate, isodecyl acrylate,lauryl acrylate, n-undecyl acrylate, stearyl acrylate, tridecylacrylate, behenyl acrylate, cyclohexyl methacrylate, cyclopentylmethacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate,2-butoxyethyl methacrylate, 2-butoxyethyl acrylate,3,3,5-trimethylcyclohexyl acrylate, 3,5-dimethyl-adamantyl acrylate,4-cumylphenyl methacrylate, cyanoethyl acrylate, cyanoethylmethacrylate, 4-biphenylyl acrylate, 4-biphenylyl methacrylate,2-naphthyl acrylate, 2-naphthyl methacrylate, tetrahydrofurfurylacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate,dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate,2-butoxyethyl acrylate, 2-butoxyethyl methacrylate, methyl3-methoxyacrylate, 3-methoxybutyl acrylate, phenoxyethyl acrylate,phenoxyethyl methacrylate, 2-phenoxyethyl methacrylate, butyl diglycolmethacrylate, ethylene glycol acrylate, ethylene glycol monomethylacrylate, methoxy-polyethylene glycol methacrylate 350,methoxy-polyethylene glycol methacrylate 500, propylene glycolmonomethacrylate, butoxydiethylene glycol methacrylate,ethoxytriethylene glycol methacrylate, octafluoropentyl acrylate,octafluoropentyl methacrylate, 2,2,2-trifluoroethyl methacrylate,1,1,1,3,3,3-hexafluoroisopropyl acrylate,1,1,1,3,3,3-hexafluoroisopropyl methacrylate,2,2,3,3,3-pentafluoropropyl methacrylate, 2,2,3,4,4,4-hexafluorobutylmethacrylate, 2,2,3,3,4,4,4-heptafluorobutyl acrylate,2,2,3,3,4,4,4-heptafluorobutyl methacrylate,2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctyl methacrylate,dimethylaminopropylacrylamide, dimethylaminopropylmethacrylamide,N-(1-methylundecyl)acrylamide, N-(n-butoxymethyl)acrylamide,N-(butoxymethyl)methacrylamide, N-(ethoxymethyl)acrylamide,N-(n-octadecyl)acrylamide, and also N,N-dialkyl-substituted amides, suchas, for example N,N-dimethylacrylamide, N,N-dimethylmethacrylamide,N-benzylacrylamides, N-isopropylacrylamide, N-tert-butylacrylamide,N-tert-octylacrylamide, N-methylolacrylamide, N-methylolmethacrylamide,acrylonitrile, methacrylonitrile, vinyl ethers, such as vinyl methylether, ethyl vinyl ether, vinyl isobutyl ether, vinyl esters, such asvinyl acetate, vinyl chloride, vinyl halides, vinylidene chloride,vinylidene halides, vinylpyridine, 4-vinylpyridine, N-vinylphthalimide,N-vinyllactam, N-vinylpyrrolidone, styrene, α- and p-methylstyrene,α-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene,3,4-dimethoxystyrene, macromonomers such as 2-polystyrene-ethylmethacrylate (weight-average molecular weight Mw, determined by GPC, of4000 to 13 000 g/mol), poly(methyl methacrylate)-ethyl methacrylate (Mwof 2000 to 8000 g/mol).

Monomers of component (c) may advantageously also be selected such thatthey include functional groups which support subsequentradiation-chemical crosslinking (by electron beams or UV, for example).Suitable copolymerizable photo initiators are, for example, benzoinacrylate and acrylate-functionalized benzophenone derivatives. Monomerswhich support crosslinking by electron bombardment are, for example,tetrahydrofurfuryl acrylate, N-tert-butylacrylamide and allyl acrylate.

The polyacrylates (“polyacrylates” are understood in the context of theinvention to be synonymous with “poly(meth)acrylates”) may be preparedby methods familiar to the skilled person, especially advantageously byconventional radical polymerizations or controlled radicalpolymerizations. The polyacrylates may be prepared by copolymerizationof the monomeric components using the customary polymerizationinitiators and also, optionally, chain transfer agents, thepolymerization being carried out at the customary temperatures in bulk,in emulsion, for example in water or liquid hydrocarbon atoms, or insolution.

The polyacrylates are prepared preferably by polymerization of themonomers in solvents, more particularly in solvents having a boilingrange of 50 to 150° C., preferably of 60 to 120° C., using the customaryamounts of polymerization initiators, which in general are 0.01 to 5,more particularly 0.1 to 2 wt %, based on the total weight of themonomers.

Suitable in principle are all customary initiators familiar to theskilled person. Examples of radical sources are peroxides,hydroperoxides and azo compounds, for example dibenzoyl peroxide, cumenehydroperoxide, cyclohexanone peroxide, di-t-butyl peroxide,cyclohexylsulfonyl acetyl peroxide, diisopropyl percarbonate, t-butylperoctoate and benzopinacol. One very preferred procedure uses asradical initiator 2,2′-azobis(2-methylbutyronitrile) (Vazo® 67™ fromDuPont) or 2,2′-azobis(2-methylpropionitrile)(2,2′-azobisisobutyronitrile; AIBN; Vazo® 64™ from DuPont).

Suitable solvents for preparing the poly(meth)acrylates include alcoholssuch as methanol, ethanol, n- and isopropanol, n- and isobutanol,preferably isopropanol and/or isobutanol, and also hydrocarbon atomssuch as toluene and, more particularly, mineral spirits with a boilingrange from 60 to 120° C. Further possibilities for use include ketonessuch as preferably acetone, methyl ethyl ketone, methyl isobutyl ketone,and esters such as ethyl acetate, and also mixtures of solvents of thetype stated, with preference being given to mixtures which compriseisopropanol, especially in amounts of 2 to 15 wt %, preferably 3 to 10wt %, based on the solvent mixture employed.

The preparation (polymerization) of the polyacrylates is followedpreferably by a concentration procedure, and the further processing ofthe polyacrylates takes place with substantial absence of solvent. Theconcentration of the polymer may be accomplished in the absence ofcrosslinker and accelerator substances. Also possible, however, is theaddition of one of these classes of compound to the polymer even priorto the concentration, in which case concentration does take place in thepresence of said substance(s).

The weight-average molecular weights Mw of the polyacrylates arepreferably in a range from 20 000 to 2 000 000 g/mol, very preferably ina range from 100 000 to 1 500 000 g/mol, most preferably in a range from150 000 to 1 000 000 g/mol. The figures for average molecular weight Mwand for polydispersity PD in this text relate to the determination bygel permeation chromatography. For that purpose it may be advantageousto carry out the polymerization in the presence of suitable chaintransfer agents such as thiols, halogen compounds and/or alcohols, inorder to set the desired average molecular weight.

The polyacrylates preferably have a K value of 30 to 90, more preferablyof 40 to 70, measured in toluene (1% strength solution, 21° C.). The Kvalue according to Fikentscher is a measure of the molecular weight andviscosity of the polymer.

Particularly suitable in accordance with the invention are polyacrylateswhich have a narrow molecular weight distribution (polydispersity PD<4).These materials in spite of a relatively low molecular weight aftercrosslinking have a particularly good shear strength. The relatively lowpolydispersity also facilitates processing from the melt, since the flowviscosity is lower than for a broader-range polyacrylate whileapplication properties are largely the same. Narrow-rangepoly(meth)acrylates can be prepared advantageously by anionicpolymerization or by controlled radical polymerization methods, thelatter being especially suitable. Via N-oxyls as well it is possible toprepare such polyacrylates. Furthermore, advantageously, Atom TransferRadical Polymerization (ATRP) may be employed for the synthesis ofnarrow-range polyacrylates, the initiator used comprising preferablymonofunctional or difunctional secondary or tertiary halides and thehalide(s) being abstracted using complexes of Cu, Ni, Fe, Pd, Pt, Ru,Os, Rh, Co, Ir, Ag or Au.

The monomers for preparing the poly(meth)acrylates preferably includeproportionally functional groups suitable for entering into linkingreactions with epoxide groups. This advantageously permits thermalcrosslinking of the polyacrylates by reaction with epoxides. Linkingreactions are understood to be, in particular, addition reactions andsubstitution reactions. Preferably, therefore, there is a linking of thebuilding blocks carrying the functional groups to building blockscarrying epoxide groups, more particularly in the sense of acrosslinking of the polymer building blocks carrying the functionalgroups via linking bridges comprising crosslinker molecules which carryepoxide groups. The substances containing epoxide groups are preferablypolyfunctional epoxides, in other words those having at least twoepoxide groups; accordingly, the overall result is preferably anindirect linking of the building blocks carrying the functional groups.

The poly(meth)acrylates of the PSA of the invention are crosslinkedpreferably by linking reactions—especially in the sense of additionreactions or substitution reactions—of functional groups they containwith thermal crosslinkers. All thermal crosslinkers may be used whichnot only ensure a sufficiently long processing life, meaning that thereis no gelling during the processing operation, particularly theextrusion operation, but also lead to rapid postcrosslinking of thepolymer to the desired degree of crosslinking at temperatures lower thanthe processing temperature, more particularly at room temperature.Possible for example is a combination of carboxyl-, amino- and/orhydroxyl-containing polymers and isocyanates, more particularlyaliphatic or trimerized isocyanates deactivated with amines, ascrosslinkers.

Suitable isocyanates are, more particularly, trimerized derivatives ofMDI [4,4-methylene-di(phenyl isocyanate)], HDI [hexamethylenediisocyanate, 1,6-hexylene diisocyanate] and/or IPDI [isophoronediisocyanate,5-isocyanato-1-isocyanatomethyl-1,3,3-trimethylcyclohexane], examplesbeing the types Desmodur® N3600 and XP2410 (each BAYER AG: aliphaticpolyisocyanates, low-viscosity HDI trimers). Likewise suitable is thesurface-deactivated dispersion of micronized trimerized IPDI BUEJ 339®,now HF9® (BAYER AG).

Also suitable in principle for the crosslinking, however, are otherisocyanates such as Desmodur VL 50 (MDI-based polyisocyanates, BayerAG), Basonat F200WD (aliphatic polyisocyanate, BASF AG), Basonat HW100(water-emulsifiable polyfunctional, HDI-based isocyanate, BASF AG),Basonat HA 300 (allophanate-modified polyisocyanate based on HDIisocyanurate, BASF) or Bayhydur VPLS2150/1 (hydrophilically modifiedIPDI, Bayer AG).

Preference is given to using thermal crosslinkers at 0.1 to 5 wt %, moreparticularly at 0.2 to 1 wt %, based on the total amount of the polymerto be crosslinked.

The poly(meth)acrylates of the PSA are crosslinked preferably by meansof one or more epoxides or one or more substances containing epoxidegroups. The substances containing epoxide groups are more particularlypolyfunctional epoxides, in other words those having at least twoepoxide groups; accordingly, the overall result is an indirect linkingof the building blocks of the poly(meth)acrylates that carry thefunctional groups. The substances containing epoxide groups may bearomatic compounds and may be aliphatic compounds.

Outstandingly suitable polyfunctional epoxides are oligomers ofepichlorohydrin, epoxy ethers of polyhydric alcohols (more particularlyethylene, propylene and butylene glycols, polyglycols, thiodiglycols,glycerol, pentaerythritol, sorbitol, polyvinyl alcohol, polyallylalcohol and the like), epoxy ethers of polyhydric phenols [moreparticularly resorcinol, hydroquinone, bis(4-hydroxyphenyl)methane,bis(4-hydroxy-3-methylphenyl)methane,bis(4-hydroxy-3,5-dibromophenyl)methane,bis(4-hydroxy-3,5-difluorophenyl)methane,1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane,2,2-bis(4-hydroxy-3-methylphenyl)propane,2,2-bis(4-hydroxy-3-chlorophenyl)propane,2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane,bis(4-hydroxyphenyl)phenylmethane, bis(4-hydroxyphenyl)diphenylmethane,bis(4-hydroxyphenyl)-4′-methylphenylmethane,1,1-bis(4-hydroxyphenyl)-2,2,2-trichloroethane,bis(4-hydroxyphenyl)(4-chlorophenyl)methane,1,1-bis(4-hydroxyphenyl)cyclohexane,bis(4-hydroxyphenyl)cyclohexylmethane, 4,4′-dihydroxybiphenyl,2,2′-dihydroxybiphenyl, 4,4′-dihydroxydiphenyl sulfone] and also theirhydroxyethyl ethers, phenol-formaldehyde condensation products, such asphenol alcohols, phenol aldehyde resins and the like, S- andN-containing epoxides (for example N,N-diglycidylaniline,N,N′-dimethyldiglycidyl-4,4-diaminodiphenylmethane) and also epoxidesprepared by customary methods from polyunsaturated carboxylic acids ormonounsaturated carboxylic esters of unsaturated alcohols, glycidylesters, polyglycidyl esters, which may be obtained by polymerization orcopolymerization of glycidyl esters of unsaturated acids or areobtainable from other acidic compounds (cyanuric acid, diglycidylsulfide, cyclic trimethylene trisulfone and/or derivatives thereof, andothers).

Very suitable ethers are, for example, 1,4-butanediol diglycidyl ether,polyglycerol-3 glycidyl ether, cyclohexanedimethanol diglycidyl ether,glycerol triglycidyl ether, neopentyl glycol diglycidyl ether,pentaerythritol tetraglycidyl ether, 1,6-hexanediol diglycidyl ether,polypropylene glycol diglycidyl ether, trimethylolpropane triglycidylether, bisphenol A diglycidyl ether and bisphenol F diglycidyl ether.

Particularly preferred for the poly(meth)acrylates as polymers to becrosslinked is the use of a crosslinker-accelerator system(“crosslinking system”) described for example in EP 1 978 069 A1, inorder to gain more effective control over not only the processing lifeand crosslinking kinetics but also the degree of crosslinking. Thecrosslinker-accelerator system comprises at least one substancecontaining epoxide groups, as crosslinker, and at least one substancewhich has an accelerating effect on crosslinking reactions by means ofepoxide-functional compounds at a temperature below the meltingtemperature of the polymer to be crosslinked, as accelerator.

Accelerators used in accordance with the invention are more preferablyamines (to be interpreted formally as substitution products of ammonia;in the formulae below, these substituents are represented by “R” andencompass in particular alkyl and/or aryl radicals and/or other organicradicals), more especially preferably those amines which enter into noreactions or only slight reactions with the building blocks of thepolymers to be crosslinked.

Selectable in principle as accelerators are primary (NRH₂), secondary(NR₂H) and tertiary (NR₃) amines, and also of course those which havetwo or more primary and/or secondary and/or tertiary amine groups.Particularly preferred accelerators, however, are tertiary amines suchas, for example, triethylamine, triethylenediamine, benzyldimethylamine,dimethylaminomethylphenol, 2,4,6-tris(N,N-dimethylaminomethyl)phenol andN,N′-bis(3-(dimethylamino)propyl)urea. As accelerators it is alsopossible with advantage to use polyfunctional amines such as diamines,triamines and/or tetramines. Outstandingly suitable arediethylenetriamine, triethylenetetramine andtrimethylhexamethylenediamine, for example.

Used with preference as accelerators, furthermore, are amino alcohols.Particular preference is given to using secondary and/or tertiary aminoalcohols, where in the case of two or more amine functionalities permolecule, preferably at least one, and preferably all, of the aminefunctionalities are secondary and/or tertiary. As preferredamino-alcohol accelerators it is possible to employ triethanolamine,N,N-bis(2-hydroxypropyl)ethanolamine, N-methyldiethanolamine,N-ethyldiethanolamine, 2-aminocyclohexanol,bis(2-hydroxycyclohexyl)methylamine, 2-(diisopropylamino)ethanol,2-(dibutylamino)ethanol, N-butyldiethanolamine, N-butylethanolamine,2-[bis(2-hydroxyethyl)amino]-2-(hydroxymethyl)-1,3-propanediol,1-[bis(2-hydroxyethyl)amino]-2-propanol, triisopropanolamine,2-(dimethylamino)ethanol, 2-(diethylamino)ethanol,2-(2-dimethylaminoethoxy)ethanol, N,N,N′-trimethyl-N′-hydroxyethylbisaminoethyl ether, N,N,N′-trimethylaminoethylethanolamine and/orN,N,N′-trimethylaminopropyl-ethanolamine.

Other suitable accelerators are pyridine, imidazoles (such as, forexample, 2-methylimidazole) and 1,8-diazabicyclo[5.4.0]undec-7-ene.Cycloaliphatic polyamines as well may be used as accelerators. Suitablealso are phosphate-based accelerators such as phosphines and/orphosphonium compounds, such as triphenylphosphine ortetraphenylphosphonium tetraphenylborate, for example.

Acrylate PSAs are typically radically polymerized copolymers of alkylesters of acrylic acid or alkyl esters of methacrylic acid with C1 toC20 alcohols such as, for example, methyl acrylate, ethyl(meth)acrylate, n-butyl (meth)acrylate, tert-butyl (meth)acrylate,cyclohexyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl(meth)acrylate, isooctyl (meth)acrylate, n-decyl (meth)acrylate,n-dodecyl (meth)acrylate, tetradecyl (meth)acrylate, lauryl(meth)acrylate, oleyl (meth)acrylate, palmityl (meth)acrylate, andstearyl (meth)acrylate, as well as other esters of (meth)acrylic acidsuch as isobornyl (meth)acrylate, benzyl (meth)acrylate, phenyl(meth)acrylate, and 2-bromoethyl (meth)acrylate, and alkoxyalkyl(meth)acrylates such as ethoxyethyl (meth)acrylate. Additionallyincluded here are esters of ethylenically unsaturated dicarboxylic andtricarboxylic acids and anhydrides such as ethyl maleate, dimethylfumarate, and ethyl methyl itaconate. Likewise included arevinylaromatic monomers such as, for example, styrene, vinyltoluene,methylstyrene, n-butylstyrene, and decylstyrene.

Further possible monomers are vinyl esters of carboxylic acidscomprising up to 20 carbon atoms, such as vinyl acetate or vinyllaurate, vinyl ethers of alcohols comprising up to 10 carbon atoms, suchas vinyl methyl ether or vinyl isobutyl ether, vinyl halides such asvinyl chloride or vinylidene dichloride, nitriles such as acrylonitrileor methacrylonitrile, acid amides such as acrylamide or methacrylamide,and unsaturated hydrocarbon atoms having 2 to 8 carbon atoms such asethylene, propene, butadiene, isoprene, 1-hexene, or 1-octene.Contemplated for the purpose of influencing the physical and opticalproperties of the PSA are polyfunctional, ethylenically unsaturatedmonomers as crosslinker monomers. Examples in this regard aredivinylbenzene, alkyl diacrylates such as 1,2-ethylene glycoldiacrylate, 1,4-butanediol diacrylate, 1,6-hexanediol diacrylate,1,8-octanediol diacrylate or 1,12-dodecanediol diacrylate, triacrylatessuch as trimethylolpropane triacrylate, and tetraacrylates such aspentaerythritol tetraacrylate. Also included among the group of thepolyfunctional monomers are UV-crosslinkable monomers, such as, forexample, (meth)acrylate-functionalized derivatives of benzophenone or ofbenzoin.

Another group of monomers are those which generate a potential forlatent crosslinking within the polymer and which, after the adhesive hasdried, lead spontaneously (frequently with catalysis) to theconstruction of a network. An example of such a monomer is glycidylmethacrylate, whose oxirane ring leads to ring opening with hydroxylfunctions or, in particular, with carboxylate functions and so to acovalent bond. This reaction takes place in accelerated form in thepresence of zinc ions or—especially when carboxyl functions arepresent—of amines.

In order for pressure-sensitive adhesive properties to be obtained, theprocessing temperature of the adhesive must be above its glasstransition temperature, in order to have viscoelastic properties.

Furthermore, acrylate-based activatable adhesives of the invention canbe used. In that case, in one particularly preferred version, theactivatable adhesives are constituted by a base polymer a) consisting of

-   a1) 40 to 95 wt % of acrylic esters and/or methacrylic esters with    the following formula CH₂═C(R₁)(COOR₂),

where R₁ is ═H or CH₃ and R₂ is ═H and/or alkyl chains having 1 to 30 Catoms

-   a2) 5 to 30 wt % of a copolymerizable vinyl monomer having at least    one carboxylic acid and/or sulfonic acid and/or phosphonic acid    group-   a3) 1 to 10 wt % of a copolymerizable vinyl monomer having at least    one epoxy group or one acid anhydride function-   a4) 0 to 20 wt % of a copolymerizable vinyl monomer which with the    functional group is able to contribute to boosted cohesion, to an    increase in the reactivity of the crosslinking, or to the direct    crosslinking, and-   b) 5 to 50 wt % of an epoxy resin or of a mixture of two or more    epoxy resins.

The polymer a) may comprise an activatable PSA which becomespressure-sensitively adhesive on exposure to temperature and,optionally, pressure, and which after bonding and cooling develops ahigh bond strength through solidification. Depending on applicationtemperature, these activatable PSAs have different static glasstransition temperatures T_(g,A) or melting points T_(m,A).

In one very preferred version, monomers used for the monomers a1) areacrylic monomers which comprise acrylic and methacrylic esters withalkyl groups consisting of 4 to 14 C atoms, preferably 4 to 9 C atoms.Specific examples, without wishing this enumeration to impose anyrestriction, are n-butyl acrylate, n-pentyl acrylate, n-hexyl acrylate,n-heptyl acrylate, n-octyl acrylate, n-nonyl acrylate, lauryl acrylate,stearyl acrylate, behenyl acrylate, and the branched isomers thereofsuch as, for example, 2-ethylhexyl acrylate. Other classes of compoundfor use, which may likewise be added in minor amounts under a1), aremethyl methacrylates, cyclohexyl methacrylates, isobornyl acrylate, andisobornyl methacrylates.

Used with preference as monomers a2) are itaconic acid, acrylic acid,methacrylic acid, vinylacetic acid, fumaric acid, crotonic acid,aconitic acid, dimethylacrylic acid, (3-acryloyloxypropionic acid,trichloroacrylic acid, vinylphosphonic acid, and vinylsulfonic acid.

Used with preference as monomers a3) are glycidyl methacrylate, maleicanhydride, and itaconic anhydride.

One very preferred version uses, for the monomers a4), vinyl esters,vinyl ethers, vinyl halides, vinylidene halides, vinyl compounds witharomatic cycles and heterocycles in α-position. Here again, withoutexclusivity, a number of examples may be given: vinyl acetate,vinylformamide, vinylpyridine, ethyl vinyl ether, vinyl chloride,vinylidene chloride, and acrylonitrile. One further very preferredversion uses, for the monomers a4), monomers having the followingfunctional groups: hydroxy, acid amide, isocyanato or amino groups.

Further particularly preferred examples for component a4) arehydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyethylmethacrylate, hydroxypropyl methacrylate, allyl alcohol, acrylamide,benzyl acrylate, benzyl methacrylate, phenyl acrylate, phenylmethacrylate, tert-butylphenyl acrylate, tert-butylphenyl methacrylate,phenoxyethyl acrylate, phenoxyethyl methacrylate, 2-butoxyethylmethacrylate, 2-butoxyethyl acrylate, dimethylaminoethyl methacrylate,dimethylaminoethyl acrylate, diethylaminoethyl methacrylate,diethylaminoethyl acrylate, cyanoethyl methacrylate, cyanoethylacrylate, 6-hydroxyhexyl methacrylate, N-tert-butylacrylamide,N-methylolmethacrylamide, N-(butoxymethyl)methacrylamide,N-methylolacrylamide, N-(ethoxymethyl)acrylamide, N-isopropylacrylamide,tetrahydrofurfuryl acrylate, this enumeration not being conclusive.

In a further preferred version, use is made, for component a4), ofaromatic vinyl compounds, in which case preferably the aromatic ringsconsist of C₄ to C₁₈ and may also include heteroatoms. Particularlypreferred examples are styrene, 4-vinylpyridine, N-vinylphthalimide,methylstyrene, 3,4-dimethoxystyrene, 4-vinylbenzoic acid, thisenumeration not being conclusive.

For the polymerization the monomers are selected in turn such that theresulting polymers can be used as industrially useful adhesives or PSAs,more particularly such that the resulting polymers have adhesive orpressure-sensitive adhesive properties in the sense of the “Handbook ofPressure Sensitive Adhesive Technology” by Donatas Satas (van Nostrand,New York 1989). Here as well the desired glass transition temperaturecan be controlled through the application of the Fox equation (E1) forthe compilation of the monomer mixture on which the polymerization isbased. For PSAs the static glass transition temperature of the resultingpolymer is advantageously below 15° C.

In order to obtain a polymer glass transition temperature T_(g,A) of≥30° C. for heat-activatable adhesive, the monomers are very preferablyselected, and the quantitative composition of the monomer mixtureadvantageously chosen, in accordance with the remarks above, in such away as to give the desired T_(g,A) value for the polymer in accordancewith the Fox equation (E1) (cf. T. G. Fox, Bull. Am. Phys. Soc. 1 (1956)123).

$\begin{matrix}{\frac{1}{T_{g}}{\sum\limits_{n}\frac{w_{n}}{T_{g,n}}}} & ({E1})\end{matrix}$

In this equation n represents the serial number of the monomers used,w_(n) the mass fraction of the respective monomer n (wt %), and T_(g,n)the respective glass transition temperature of the homopolymer of therespective monomers n in K.

For the preparation of the adhesives, advantageously, conventionalradical polymerizations or controlled radical polymerizations arecarried out. For the polymerizations proceeding by a radical route,preference is given to using initiator systems which further compriseother radical initiators for the polymerization, especially thermallydecomposing radical-forming azo or peroxo initiators. Suitable inprinciple, however, are all of the initiators that are typical foracrylates and familiar to the skilled person. The production ofC-centered radicals is described in Houben Weyl, Methoden derOrganischen Chemie, Vol. E 19a, pages 60 to 147. These methods arepreferentially employed analogously.

Examples of radical sources are peroxides, hydroperoxides, and azocompounds; certain nonexclusive examples of typical radical initiatorsmay be given here as potassium peroxodisulfate, dibenzoyl peroxide,cumene hydroperoxide, cyclohexanone peroxide, di-tert-butyl peroxide,azodiisobutyronitrile, cyclohexylsulfonyl acetyl peroxide, diisopropylpercarbonate, tert-butyl peroctoate, and benzopinacol. One verypreferred version uses 1,1′-azobis(cyclohexanecarbonitrile) (Vazo88™from DuPont) as radical initiator.

The average molecular weights M_(n) of the PSAs resulting from theradical polymerization are very preferably selected such that they arein a range from 20 000 to 2 000 000 g/mol; specifically for further useas pressure-sensitive hotmelt adhesives, PSAs are prepared that haveaverage molecular weights M_(n) of 100 000 to 500 000 g/mol.

The polymerization can be conducted in bulk, in the presence of one ormore organic solvents, in the presence of water, or in mixtures oforganic solvents and water. The aim here is to minimize the amount ofsolvent used.

Depending on conversion and temperature, the polymerization time isbetween 4 and 72 hours. The higher the level at which it is possible toselect the reaction temperature, in other words the higher the thermalstability of the reaction mixture, the lower the reaction time can be.

If low flammability is desirable, it can be achieved by adding flameretardants to the adhesive. These may be organic bromine compounds, asand when required with synergists such as antimony trioxide, although inrelation to the absence of halogen from the adhesive tape, preference isgiving to using red phosphorus, organophosphorous compounds, mineralcompounds or intumescent compounds such as ammonium polyphosphate aloneor in conjunction with synergists. A comprehensive description ofsuitable flame retardants is given later.

The adhesive coat weight is preferably between 80 and 160 g/m², morepreferably between 90 and 100 g/m².

In order to increase the cohesion between the adhesive and the adjacentlayer, the adhesive and/or the adjacent layer may be subjected to acorona treatment.

Primers as well may be used to improve the promotion of adhesion.Descriptions of the primers customarily used are found for example in“Handbook of Pressure Sensitive Adhesive Technology” by Donatas Satas(van Nostrand, 1989).

The fourth layer, which is formed by a flame-retardant foam having athickness of at least 0.5 to 3 mm, more preferably 1 to 2 mm, is a layerof a polymer foam. This refers to a foam whose matrix material is formedsubstantially of one or more polymers. The matrix material of the foamedlayer preferably comprises one or more polymers to an extent of at least30 wt %, more preferably at least 50 wt % and very preferably at least70 wt %, more particularly at least 90 wt %, based in each case on thetotal weight of the foamed layer. The polymers of the polymer foam arepreferably selected from the group consisting of polyolefins;polyurethanes; polyvinyl chloride (PVC); terpolymers of ethylene,propylene and a non-conjugated diene (EPDM); copolymers of ethylene andan ethylene substituted by a polar group; polyacrylates; and alsomixtures of two or more of the aforesaid polymers. Accordingly thematrix material of the foamed layer comprises one or more polymers to anextent of preferably at least 30 wt %, more preferably at least 50 wt %and very preferably at least 70 wt %, more particularly at least 90 wt%, based in each case on the total weight of the foamed layer, said oneor more polymers being selected from the group consisting ofpolyolefins; polyurethanes; polyvinyl chloride (PVC); terpolymers ofethylene, propylene and a non-conjugated diene (EPDM); copolymers ofethylene and an ethylene substituted by a polar group; polyacrylates;and also mixtures of two or more of the aforesaid polymers. Withparticular preference the foamed layer comprises no further polymersother than one or more polymers selected from the group consisting ofpolyolefins; polyurethanes; polyvinyl chloride (PVC); terpolymers ofethylene, propylene and a non-conjugated diene (EPDM); copolymers ofethylene and an ethylene substituted by a polar group; polyacrylates;and also mixtures of two or more of the aforesaid polymers.

With particular preference the polymer foam or the foamed layercomprises at least one polyurethane polymer. More particularly thefraction of the entirety of all the polyurethane polymers in the foamedlayer is at least 30 wt %, more preferably at least 50 wt % and verypreferably at least 70 wt %, more particularly at least 80 wt %, as forexample at least 90 wt %, based in each case on the total weight of thefoamed layer. With very particular preference the foamed layer containsno further polymers.

A “polyolefin” in the invention is a polymer of the general structure—[CH₂—CR¹R²—]_(n)—, in which R¹ and R² independently of one another area hydrogen atom or a linear or branched, saturated, aliphatic orcycloaliphatic group. The polyolefin is preferably polyethylene,polypropylene, an ethylene-propylene copolymer or a mixture ofpolyethylene and polypropylene. The polyethylene here may comprise oneor more of the types of polyethylene known per se, such as HDPE, LDPE,LLDPE, VLDPE, VLLDPE, blends of these types of polyethylene, andmixtures thereof. The polypropylene is preferably a crystallinepolypropylene, more preferably a homopolypropylene (hPP). In onespecific embodiment of the invention the foamed layer contains no otherpolymers apart from one or more polyolefins.

A copolymer of ethylene and an ethylene substituted by a polar grouprefers to a polymer of the general structure —[CH₂—CR³R⁴—]_(n)—, inwhich R³ or R⁴ is a hydrogen atom and the remaining substituent in eachcase is a group containing at least one oxygen atom. The copolymer ofethylene and an ethylene substituted by a polar group is preferably anethylene-vinyl acetate copolymer (EVA), an ethylene-methyl acrylatecopolymer (EMA), an ethylene-ethyl acrylate copolymer (EEA), anethylene-acrylic acid copolymer (EAA), an ethylene-butyl acrylatecopolymer (EBA) or a mixture of these. More preferably the copolymer ofethylene and an ethylene substituted by a polar group is anethylene-vinyl acetate copolymer (EVA). The EVA preferably has a vinylacetate content of 3 to 70 wt %, more preferably of 5 to 30 wt %, moreparticularly of 10 to 20 wt %. In one specific embodiment of theinvention the foamed layer contains no further polymers apart from oneor more copolymers of ethylene and an ethylene substituted by a polargroup, more particularly no further polymers apart from anethylene-vinyl acetate copolymer (EVA).

The foaming of the matrix material may in principle have been broughtabout in any customary way, as for example by an added blowing gas or bya chemical foaming agent which decomposes during processing at a definedtemperature and, in so doing, forms gas.

PE foams are frequently produced by mixing the customarily pulverulentfoaming agent and the polymer in a first step. This mixture constituteswhat is called the masterbatch. Then, in the next step, the othercomponents of the foam are mixed in, examples being residual polymers,ageing inhibitors, optionally flame retardants, etc. For this purpose itis possible to use extruders, such as twin-screw extruders, for example,or kneading apparatus.

In a further process step, the mixture is then extruded to form a foamedmatrix, in a single-screw extruder, for example, and this matrix isdischarged as a layer through a die. The result is what is called a filmbale. The composition is subsequently crosslinked, by means for exampleof electron beam curing using an electron beam accelerator.

Then, in a final step, foaming takes place, frequently in the form ofthermal foaming, i.e. foaming initiated by thermal activation of thefoaming agent.

In accordance with the invention the foamed layer contains a flameretardant with an amount of at least 1 wt % of flame retardant andpreferably less than 10 wt % of flame retardant. It has emerged thatwith levels of flame retardant of this kind, there is no adverse effect,or virtually none, on the properties of the foamed layer. In theinvention, the lower the fractions of flame retardant in the foamedlayer, the greater the preference according to such fractions. Thefoamed layer contains preferably less than 8 wt %, more preferably lessthan 6 wt %, more particularly less than 3 wt %. The figures are basedin each case on the total weight of the foam layer.

Flame retardants which can be used include, for example, aluminum oxidehydrates, zinc borates, ammonium phosphates and/or ammoniumpolyphosphates, antimony oxide, chlorinated paraffins, polychlorinatedbiphenyls, hexabrombenzene, polybrominated diphenyl ethers; cyanuratessuch as melaminecyanurate; organic phosphoric acid derivatives, as forexample 2-carboxyethyl-phenylphosphoric acid; organic phosphates andpolyphosphates, phosphites and phosphonates, as for example tritolylphosphate, tert-butylphenyl diphenyl phosphate, bisphenol A-bis(diphenylphosphate), resorcinol bis(diphenyl phosphate) and melaminepolyphosphate, diethyl bis(2-hydroxyethyl)aminomethylphosphonate anddiphenyl anilinophosphonate; phosphinic salts, diphosphinic salts anddialkylphosphinic salts; and also halogenated organic phosphoruscompounds such as tris(2,3-dibrompropyl) phosphate,tris(2-brom-4-methylphenyl) phosphate and tris(2-chlorisopropyl)phosphate. Halogen-free flame retardants are preferred in the invention.The flame retardants which can be used in the invention are thereforepreferably selected from the group consisting of aluminum oxidehydrates, zinc borates, ammonium phosphates and ammonium polyphosphates,antimony oxide; cyanurates; organic phosphoric acid derivatives; organicphosphates, phosphites and phosphonates; phosphinic salts, disphosphinicsalts and dialkyl phosphinic salts, and also mixtures of two or more ofthe above-recited flame retardants. More preferably the flame retardantswhich can be used in the invention are selected from the groupconsisting of ammonium polyphosphates and dialkyl phosphinic salts.

Dialkyl phosphinic salts preferred in the invention are those of theformula F2

(R^(III)R^(IV)(O)P—O⁽⁻⁾)_(m)M^((m+))  (F2),

in which R^(III) and R^(IV) are identical or different and are a linearor branched C₁- to C₆ alkyl radical;

M is Mg, Ca, Al, Sb, Sn, Ge, Ti, Fe, Zr, Zn, Ce, Bi, Sr, Mn, Li, Na, Kor a protonated nitrogen base; and

m is a natural number from 1 to 4.

M is preferably Al, Ca, Ti, Zn, Sn or Zr.

R^(III) and R^(IV) are preferably identical or different and are amethyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl,n-pentyl, isopentyl, n-hexyl or isohexyl radical.

Particularly preferred dialkyl phosphinic salts are aluminum trisdiethylphosphinate, aluminum trismethylethyl phosphinate, aluminumtrisethylbutyl phosphinate, titanyl bisdiethyl phosphinate, titaniumtetrakisdiethyl phosphinate, titanyl bismethylethyl phosphinate,titanium tetrakismethylethyl phosphinate, titanyl bisethylbutylphosphinate, titanium tetrakisethylbutyl phosphinate, zinc bisdiethylphosphinate, zinc bismethylethyl phosphinate and zinc bisethylbutylphosphinate, and also mixtures of one or more of these dialkylphosphinic salts.

Besides the substances already mentioned, the flame retardant may in theinvention comprise one or more substances known as synergists.Synergists may be present at 0.1 to 70 wt % in the flame retardant,based on the total weight of the flame retardant. More preferably theflame retardant comprises

a) 60 to 99 wt % of one or more compounds selected from dialkylphosphinic salts of the formula

F2 and ammonium polyphosphates, and

b) 1 to 40 wt % of one or more synergists, the fractions being based onthe total weight of the flame retardant and adding up to 100 wt %.

The synergists are preferably compounds of nitrogen, of phosphorus or ofnitrogen and phosphorus. More preferably the synergist or synergists isor are selected from the group consisting of allantoin, cyanuric acid,glycoluril, urea, melamine, melam, melem, melon, melamine phosphate,melamine pyrophosphate, melamine polyphosphate, melam polyphosphate,melem polyphosphate, melon polyphosphate, melamine cyanurate, piperazinephosphate, piperazine pyrophosphate, carbodiimide, sterically hinderedphenols, phosphine oxide, hypophosphite, cyclic phosphonates,triaryl(alkyl) phosphites, alkyl- and aryl-substituted phosphates,compounds of aluminum, of tin, of boron, of magnesium, of calcium and ofcerium, zinc oxide, zinc carbonate, zinc stannate, zinc borate, zinchydrogen phosphate, zinc pyrophosphate, zinc oleate, zinc stearateand/or zinc phosphate.

Where the flame retardant comprises one or more synergists, they areregarded in the invention as part of the flame retardant. If present,therefore, they are included in particular as well in the fractions offlame retardant mentioned in preceding sections.

The flame retardant may be incorporated into the compositions of thefoamed layer using customary mixing devices, such as with agitatormechanisms, for example. Incorporation takes place preferably before thelayer in question is applied.

Furthermore, silicone-based additives may be added which support theeffect of the flame retardants. Such additives are described for examplein U.S. Pat. No. 4,387,176 A.

The fifth layer, which is formed by a second, acrylate-basedpressure-sensitive adhesive with a basis weight of 300 to 1500 g/m²,preferably 360 to 1500 g/m², more preferably 600 to 1200 g/m² and/or athickness of 400 to 1800 μm, preferably 500 to 1500 μm, more preferably800 to 1200 μm, is preferably a foamed, acrylate-based adhesive, of thekind available for example from tesa under the designation ACX^(plus).

The ACX^(plus) range encompasses single-ply or multi-ply adhesive tapeswhich have foamed, acrylate-based adhesives.

Adhesive tapes of this kind preferably have a carrier layer which isalso referred to as the hard phase. The polymer basis of the hard phaseis preferably selected from the group consisting of polyvinyl chlorides(PVC), polyethylene terephthalates (PET), polyurethanes, polyolefins,polybutylene terephthalates (PBT), polycarbonates, polymethylmethacrylates (PMMA), polyvinyl butyrals (PVB), ionomers, and mixturesof two or more of the above-recited polymers.

More preferably the polymer basis of the hard phase is selected from thegroup consisting of polyvinyl chlorides, polyethylene terephthalates,polyurethanes, polyolefins, and mixtures of two or more of theabove-recited polymers. The hard phase is essentially a polymer filmwhose polymer basis is selected from the materials above. A “polymerfilm” is a thin, sheetlike, flexible, windable web whose material basisis formed substantially of one or more polymers.

“Polyurethanes” in the broad sense are polymeric substances in whichrepeating units are linked to one another by urethane moieties—NH—CO—O—.

“Polyolefins” are polymers which on an amount-of-substance basis containat least 50% of repeating units of the general structure—[—CH2-CR1R2-]n-, in which R1 is a hydrogen atom and R2 is a hydrogenatom or is a linear or branched, saturated aliphatic or cycloaliphaticgroup. Where the polymer basis of the hard phase comprises polyolefins,these olefins are more preferably polyethylenes, more particularlyultra-high molar mass polyethylenes (UHMWPE).

The “polymer basis” is understood to be the polymer or polymers makingup the greatest weight fraction of all the polymers present in therelevant layer or phase.

The thickness of the hard phase is in particular ≤150 μm. The thicknessof the hard phase is preferably 10 to 150 μm, more preferably 30 to 120μm and more particularly 50 to 100 μm, as for example 70 to 85 μm. The“thickness” refers to the extent of the relevant layer or phase alongthe z-ordinate of an imagined coordinate system in which the x-y planeis formed by the plane spanned by the machine direction and the crossdirection to the machine direction. The thickness is ascertained bymeasurement at not less than five different places on the relevant layeror phase, with subsequent formation of the arithmetic mean from themeasurement results obtained. The thickness of the hard phase ismeasured here in agreement with DIN EN ISO 4593.

Adhesive tapes of this kind may also have a soft phase, comprising apolymer foam, a viscoelastic mass and/or an elastomeric mass. Thepolymer basis of the soft phase is preferably selected from polyolefins,polyacrylates, polyurethanes, and mixtures of two or more of theabove-recited polymers.

In the simplest version the adhesive tape consists only of a soft phase.

A “polymer foam” is a structure composed of gas-filled spherical orpolyhedral cells which are bounded by liquid, semi-liquid,high-viscosity or solid cell struts; furthermore, the main constituentof the cell struts is a polymer or a mixture of two or more polymers.

A “viscoelastic mass” refers to a material which as well as exhibitingfeatures of pure elasticity (return to the original state after externalmechanical exposure) also exhibits features of a viscous liquid, such asthe occurrence of internal friction on deformation. Polymer-based PSAsin particular are regarded as being viscoelastic masses.

An “elastomeric mass” refers to a material which exhibits rubber-elasticbehavior and which at 20° C. can be stretched repeatedly to at leasttwice its length and, when the force needed for the stretching isremoved, immediately reoccupies dimensions close to its startingdimensions.

As regards the understanding of the terms “polymer basis”,“polyurethanes” and “polyolefins”, the definitions above are valid.“Polyacrylates” are polymers whose monomer basis consists to an extentof at least 50%, on an amount-of-substance basis, of acrylic acid,methacrylic acid, acrylic esters and/or methacrylic esters, with acrylicesters and/or methacrylic esters being included at least proportionally,in general and preferably, at not less than 50%. More particularly a“polyacrylate” is a polymer obtainable by radical polymerization ofacrylic and/or methyl acrylic monomers and also, optionally, further,copolymerizable monomers.

With particular preference the polymer basis of the soft phase isselected from polyolefins, polyacrylates and mixtures of two or more ofthe above-recited polymers. Where polyolefins form part of the polymerbasis of the soft phase, they are preferably selected frompolyethylenes, ethylene-vinyl acetate copolymers (EVA) and mixtures ofpolyethylenes and ethylene-vinyl acetate copolymers (PE/EVA blends).These polyethylenes may be different types of polyethylene, as forexample HDPE, LDPE, LLDPE, blends of these polyethylene types and/ormixtures thereof.

In one embodiment the soft phase comprises a foam and apressure-sensitive adhesive layer disposed respectively above and belowthe foamed layer, with the polymer basis of the foam consisting of oneor more polyolefins, and the polymer basis of the pressure-sensitiveadhesive layers consisting of one or more polyacrylates. More preferablythe polymer basis of this foam consists of one or more polyethylenes,ethylene-vinyl acetate copolymer(s) and mixtures of one or morepolyethylene(s) and/or ethylene-vinyl acetate copolymer(s). Verypreferably the polymer basis of this foam consists of one or morepolyethylenes.

The polyolefin-based foam itself has only very little pressure-sensitiveadhesiveness, or none. The bond with the hard phase or with thesubstrate is therefore brought about advantageously through thepressure-sensitive adhesive layers. The foaming of the polyolefin-basedstarting material of the foam is brought about preferably by addedblowing gas in a physical foaming process, and/or by means of a chemicalfoaming agent, as for example by azodicarbonamide.

In another embodiment, the soft phase is a pressure-sensitive adhesivepolymer foam whose polymer basis consists of one or more polyacrylates.“Pressure-sensitive adhesive foam” means that the foam itself is a PSAand there is therefore no need for an additional pressure-sensitiveadhesive layer to be applied. This is advantageous because in theproduction operation there are fewer layers to be assembled and the riskof detachment phenomena and of other unwanted manifestations at thelayer boundaries is reduced.

The polyacrylates are preferably obtainable by at least proportionalcopolymerization of functional monomers which are crosslinkable withepoxide groups. These monomers are more preferably those with acidgroups (particularly carboxylic, sulfonic or phosphonic acid groups)and/or hydroxyl groups and/or acid anhydride groups and/or epoxidegroups and/or amine groups; especially preferred are monomers containingcarboxylic acid groups. It is particularly advantageous for thepolyacrylates to contain copolymerized acrylic acid and/or methacrylicacid. All of these groups feature crosslinkability with epoxide groups,thereby making the polyacrylates amenable advantageously to thermalcrosslinking with introduced epoxides.

Other monomers which may be used as comonomers for the polyacrylates,aside from acrylic and/or methacrylic esters having up to 30 carbonatoms, are, for example, vinyl esters of carboxylic acids containing upto 20 carbon atoms, vinyl aromatics having up to 20 carbon atoms,ethylenically unsaturated nitriles, vinyl halides, vinyl ethers ofalcohols containing 1 to 10 carbon atoms, aliphatic hydrocarbon atomshaving 2 to 8 carbon atoms and one or two double bonds, or mixtures ofthese monomers.

The properties of the polyacrylate in question may be influenced inparticular by variation in the glass transition temperature of thepolymer through different weight fractions of the individual monomers.The polyacrylates may be derived preferably from the following monomercomposition:

-   -   a) acrylic esters and/or methacrylic esters of the following        formula

CH₂═C(R^(I))(COOR^(II))

-   -   -   where R^(I) is ═H or CH₃ and R^(II) is an alkyl radical            having 4 to 14 carbon atoms,

    -   b) olefinically unsaturated monomers having functional groups of        the kind already defined for reactivity with epoxide groups,

    -   c) optionally further acrylates and/or methacrylates and/or        olefinically unsaturated monomers which are copolymerizable with        component (a).

The polyacrylates derive preferably from a monomer composition in whichthe monomers of component (a) are present with a fraction of 45 to 99 wt%, the monomers of component (b) with a fraction of 1 to 15 wt % and themonomers of component (c) with a fraction of 0 to 40 wt % (the figuresare based on the monomer mixture for the “base polymer”, i.e. withoutadditions of possible additives to the completed polymer, such asresins, etc.). In this case the polymerization product has a glasstransition temperature of 15° C. (DMA at low frequencies) andpressure-sensitive adhesive properties.

The monomers of component (a) are more particularly plasticizing and/ornon-polar monomers. Used preferably as monomers (a) are acrylic andmethacrylic esters having alkyl groups consisting of 4 to 14 carbonatoms, more preferably 4 to 9 carbon atoms. Examples of such monomersare n-butyl acrylate, n-butyl methacrylate, n-pentyl acrylate, n-pentylmethacrylate, n-amyl acrylate, n-hexyl acrylate, n-hexyl methacrylate,n-heptyl acrylate, n-octyl acrylate, n-octyl methacrylate, n-nonylacrylate, isobutyl acrylate, isooctyl acrylate, isooctyl methacrylate,and their branched isomers, such as, for example, 2-ethylhexyl acrylateor 2-ethylhexyl methacrylate.

The monomers of component (b) are more particularly olefinicallyunsaturated monomers having functional groups, especially havingfunctional groups able to enter into a reaction with epoxide groups.

Used preferably for component (b) are monomers having functional groupsselected from the group encompassing the following: hydroxyl, carboxyl,sulfonic acid or phosphonic acid groups, acid anhydrides, epoxides,amines.

Particularly preferred examples of monomers of component (b) are acrylicacid, methacrylic acid, itaconic acid, maleic acid, fumaric acid,crotonic acid, aconitic acid, dimethylacrylic acid,β-acryloyloxypropionic acid, trichloroacrylic acid, vinyl acetic acid,vinyl phosphonic acid, maleic anhydride, hydroxyethyl acrylate,hydroxypropyl acrylate, hydroxyethyl methacrylate, hydroxypropylmethacrylate, 6-hydroxyhexyl methacrylate, allyl alcohol, glycidylacrylate, glycidyl methacrylate.

In principle it is possible as component (c) to use all vinylicallyfunctionized compounds which are copolymerizable with component (a)and/or with component (b). The monomers of component (c) may serve toadjust the properties of the resultant PSA.

Illustrative monomers of component (c) are as follows:

methyl acrylate, ethyl acrylate, propyl acrylate, methyl methacrylate,ethyl methacrylate, benzyl acrylate, benzyl methacrylate, sec-butylacrylate, tert-butyl acrylate, phenyl acrylate, phenyl methacrylate,isobornyl acrylate, isobornyl methacrylate, tert-butylphenyl acrylate,tert-butylphenyl methacrylate, dodecyl methacrylate, isodecyl acrylate,lauryl acrylate, n-undecyl acrylate, stearyl acrylate, tridecylacrylate, behenyl acrylate, cyclohexyl methacrylate, cyclopentylmethacrylate, phenoxyethyl acrylate, phenoxyethyl methacrylate,2-butoxyethyl methacrylate, 2-butoxyethyl acrylate,3,3,5-trimethylcyclohexyl acrylate, 3,5-dimethyl-adamantyl acrylate,4-cumylphenyl methacrylate, cyanoethyl acrylate, cyanoethylmethacrylate, 4-biphenylyl acrylate, 4-biphenylyl methacrylate,2-naphthyl acrylate, 2-naphthyl methacrylate, tetrahydrofurfurylacrylate, diethylaminoethyl acrylate, diethylaminoethyl methacrylate,dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate,2-butoxyethyl acrylate, 2-butoxyethyl methacrylate, methyl3-methoxyacrylate, 3-methoxybutyl acrylate, phenoxyethyl acrylate,phenoxyethyl methacrylate, 2-phenoxyethyl methacrylate, butyl diglycolmethacrylate, ethylene glycol acrylate, ethylene glycol monomethylacrylate, methoxy-polyethylene glycol methacrylate 350,methoxy-polyethylene glycol methacrylate 500, propylene glycolmonomethacrylate, butoxydiethylene glycol methacrylate,ethoxytriethylene glycol methacrylate, octafluoropentyl acrylate,octafluoropentyl methacrylate, 2,2,2-trifluoroethyl methacrylate,1,1,1,3,3,3-hexafluoroisopropyl acrylate,1,1,1,3,3,3-hexafluoroisopropyl methacrylate,2,2,3,3,3-pentafluoropropyl methacrylate, 2,2,3,4,4,4-hexafluorobutylmethacrylate, 2,2,3,3,4,4,4-heptafluorobutyl acrylate,2,2,3,3,4,4,4-heptafluorobutyl methacrylate,2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctyl methacrylate,dimethylaminopropylacrylamide, dimethylaminopropylmethacrylamide,N-(1-methylundecyl)acrylamide, N-(n-butoxymethyl)acrylamide,N-(butoxymethyl)methacrylamide, N-(ethoxymethyl)acrylamide,N-(n-octadecyl)acrylamide, and also N,N-dialkyl-substituted amides, suchas, for example N,N-dimethylacrylamide, N,N-dimethylmethacrylamide,N-benzylacrylamides, N-isopropylacrylamide, N-tert-butylacrylamide,N-tert-octylacrylamide, N-methylolacrylamide, N-methylolmethacrylamide,acrylonitrile, methacrylonitrile, vinyl ethers, such as vinyl methylether, ethyl vinyl ether, vinyl isobutyl ether, vinyl esters, such asvinyl acetate, vinyl chloride, vinyl halides, vinylidene chloride,vinylidene halides, vinylpyridine, 4-vinylpyridine, N-vinylphthalimide,N-vinyllactam, N-vinylpyrrolidone, styrene, α- and p-methylstyrene,α-butylstyrene, 4-n-butylstyrene, 4-n-decylstyrene,3,4-dimethoxystyrene, macromonomers such as 2-polystyrene-ethylmethacrylate (molecular weight M_(w) of 4000 to 13 000 g/mol),poly(methyl methacrylate)-ethyl methacrylate (Mw of 2000 to 8000 g/mol).

Monomers of component (c) may advantageously also be selected such thatthey include functional groups which support subsequentradiation-chemical crosslinking (by electron beams or UV, for example).Suitable copolymerizable photo initiators are, for example, benzoinacrylate and acrylate-functionalized benzophenone derivatives. Monomerswhich support crosslinking by electron bombardment are, for example,tetrahydrofurfuryl acrylate, N-tert-butylacrylamide and allyl acrylate.

The polyacrylates (“polyacrylates” are understood in the context of theinvention to be synonymous with “poly(meth)acrylates”) may be preparedby methods familiar to the skilled person, especially advantageously byconventional radical polymerizations or controlled radicalpolymerizations. The polyacrylates may be prepared by copolymerizationof the monomeric components using the customary polymerizationinitiators and also, optionally, chain transfer agents, thepolymerization being carried out at the customary temperatures in bulk,in emulsion, for example in water or liquid hydrocarbon atoms, or insolution.

The polyacrylates are prepared preferably by polymerization of themonomers in solvents, more particularly in solvents having a boilingrange of 50 to 150° C., preferably of 60 to 120° C., using the customaryamounts of polymerization initiators, which in general are 0.01 to 5,more particularly 0.1 to 2 wt % (based on the total weight of themonomers).

Suitable in principle are all customary initiators familiar to theskilled person. Examples of radical sources are peroxides,hydroperoxides and azo compounds, for example dibenzoyl peroxide, cumenehydroperoxide, cyclohexanone peroxide, di-t-butyl peroxide,cyclohexylsulfonyl acetyl peroxide, diisopropyl percarbonate, t-butylperoctoate and benzopinacol. One very preferred procedure uses asradical initiator 2,2′-azobis(2-methylbutyronitrile) (Vazo® 67™ fromDuPont) or 2,2′-azobis(2-methylpropionitrile)(2,2′-azobisisobutyronitrile; AIBN; Vazo® 64™ from DuPont).

Suitable solvents for preparing the polyacrylates include alcohols suchas methanol, ethanol, n- and isopropanol, n- and isobutanol, preferablyisopropanol and/or isobutanol, and also hydrocarbon atoms such astoluene and, more particularly, mineral spirits with a boiling rangefrom 60 to 120° C. Further possibilities for use include ketones such aspreferably acetone, methyl ethyl ketone, methyl isobutyl ketone, andesters such as ethyl acetate, and also mixtures of solvents of the typestated, with preference being given to mixtures which compriseisopropanol, especially in amounts of 2 to 15 wt %, preferably 3 to 10wt %, based on the solvent mixture employed.

The preparation (polymerization) of the polyacrylates is followedpreferably by a concentration procedure, and the further processing ofthe polyacrylates takes place with substantial absence of solvent. Theconcentration of the polymer may be accomplished in the absence ofcrosslinker and accelerator substances. Also possible, however, is theaddition of one of these classes of compound to the polymer even priorto the concentration, in which case concentration does take place in thepresence of said substance(s).

After the concentration step, the polymers may be transferred to acompounder. It is possible as an option for concentration andcompounding to take place in the same reactor as well.

The weight-average molecular weights Mw of the polyacrylates arepreferably in a range from 20 000 to 2 000 000 g/mol, very preferably ina range from 100 000 to 1 000 000 g/mol, most preferably in a range from150 000 to 500 000 g/mol. For that purpose it may be advantageous tocarry out the polymerization in the presence of suitable chain transferagents such as thiols, halogen compounds and/or alcohols, in order toset the desired average molecular weight.

The polyacrylate preferably has a K value of 30 to 90, more preferablyof 40 to 70, measured in toluene (1% strength solution, 21° C.). The Kvalue according to Fikentscher is a measure of the molecular weight andviscosity of the polymer.

Particularly suitable are polyacrylates which have a narrow molecularweight distribution (polydispersity PD<4). These materials in spite of arelatively low molecular weight after crosslinking have a particularlygood shear strength. The relatively low polydispersity also facilitatesprocessing from the melt, since the flow viscosity is lower than for abroader-range polyacrylate while application properties are largely thesame. Narrow-range poly(meth)acrylates can be prepared advantageously byanionic polymerization or by controlled radical polymerization methods,the latter being especially suitable. Examples of polyacrylates of thiskind prepared by the RAFT process are described in U.S. Pat. No.6,765,078 B2 and U.S. Pat. No. 6,720,399 B2. Via N-oxyls as well it ispossible to prepare such polyacrylates, as described, for example, in EP1 311 555 B1. Furthermore, advantageously, Atom Transfer RadicalPolymerization (ATRP) may be employed for the synthesis of narrow-rangepolyacrylates, the initiator used comprising preferably monofunctionalor difunctional secondary or tertiary halides and the halide(s) beingabstracted using complexes of Cu, Ni, Fe, Pd, Pt, Ru, Os, Rh, Co, Ir, Agor Au. The various possibilities of the ATRP are described inspecifications U.S. Pat. Nos. 5,945,491 A, 5,854,364 A and 5,789,487 A.

The monomers for preparing the polyacrylates preferably includeproportionally functional groups suitable for entering into linkingreactions with epoxide groups. This advantageously permits thermalcrosslinking of the polyacrylates by reaction with epoxides. Linkingreactions are understood to be, in particular, addition reactions andsubstitution reactions. Preferably, therefore, there is a linking of thebuilding blocks carrying the functional groups to building blockscarrying epoxide groups, more particularly in the sense of acrosslinking of the polymer building blocks carrying the functionalgroups via linking bridges comprising crosslinker molecules which carryepoxide groups. The substances containing epoxide groups are preferablypolyfunctional epoxides, in other words those having at least twoepoxide groups; accordingly, the overall result is preferably anindirect linking of the building blocks carrying the functional groups.

The polyacrylate or polyacrylates are crosslinked preferably by linkingreactions—especially in the sense of addition reactions or substitutionreactions—of functional groups they contain with thermal crosslinkers.All thermal crosslinkers may be used which not only ensure asufficiently long processing life, meaning that there is no gellingduring the processing operation, but also lead to rapid postcrosslinkingof the polymer to the desired degree of crosslinking at temperatureslower than the processing temperature, more particularly at roomtemperature. Possible for example is a combination of carboxyl-, amino-and/or hydroxyl-containing polymers and isocyanates, as crosslinkers,more particularly the aliphatic or amine-deactivated trimerizedisocyanates described in EP 1 791 922 A1.

Suitable isocyanates are, more particularly, trimerized derivatives ofMDI [4,4-methylene-di(phenyl isocyanate)], HDI [hexamethylenediisocyanate, 1,6-hexylene diisocyanate] and/or

IPDI [isophorone diisocyanate,5-isocyanato-1-isocyanatomethyl-1,3,3-trimethylcyclohexane], examplesbeing the types Desmodur® N3600 and XP2410 (each BAYER AG: aliphaticpolyisocyanates, low-viscosity HDI trimers). Likewise suitable is thesurface-deactivated dispersion of micronized trimerized IPDI BUEJ 339®,now HF9® (BAYER AG).

Also suitable in principle for the crosslinking, however, are otherisocyanates such as Desmodur VL 50 (MDI-based polyisocyanates, BayerAG), Basonat F200WD (aliphatic polyisocyanate, BASF AG), Basonat HW100(water-emulsifiable polyfunctional, HDI-based isocyanate, BASF AG),Basonat HA 300 (allophanate-modified polyisocyanate based on HDIisocyanurate, BASF) or Bayhydur VPLS2150/1 (hydrophilically modifiedIPDI, Bayer AG). Preference is given to using the thermal crosslinker,for example the trimerized isocyanate, at 0.1 to 5 wt %, moreparticularly at 0.2 to 1 wt %, based on the total amount of the polymerto be crosslinked.

The thermal crosslinker preferably comprises at least one substancecontaining epoxide groups. The substances containing epoxide groups aremore particularly polyfunctional epoxides, in other words those havingat least two epoxide groups; accordingly, the overall result is anindirect linking of the building blocks that carry the functionalgroups. The substances containing epoxide groups may be aromaticcompounds and may be aliphatic compounds.

Outstandingly suitable polyfunctional epoxides are oligomers ofepichlorohydrin, epoxy ethers of polyhydric alcohols (more particularlyethylene, propylene and butylene glycols, polyglycols, thiodiglycols,glycerol, pentaerythritol, sorbitol, polyvinyl alcohol, polyallylalcohol and the like), epoxy ethers of polyhydric phenols [moreparticularly resorcinol, hydroquinone, bis(4-hydroxyphenyl)methane,bis(4-hydroxy-3-methylphenyl)methane,bis(4-hydroxy-3,5-dibromophenyl)methane,bis(4-hydroxy-3,5-difluorophenyl)methane,1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)propane,2,2-bis(4-hydroxy-3-methylphenyl)propane,2,2-bis(4-hydroxy-3-chlorophenyl)propane,2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane,bis(4-hydroxyphenyl)phenylmethane, bis(4-hydroxyphenyl)diphenylmethane,bis(4-hydroxyphenyl)-4′-methylphenylmethane,1,1-bis(4-hydroxyphenyl)-2,2,2-trichloroethane,bis(4-hydroxyphenyl)(4-chlorophenyl)methane,1,1-bis(4-hydroxyphenyl)cyclohexane,bis(4-hydroxyphenyl)cyclohexylmethane, 4,4′-dihydroxybiphenyl,2,2′-dihydroxybiphenyl, 4,4′-dihydroxydiphenyl sulfone] and also theirhydroxyethyl ethers, phenol-formaldehyde condensation products, such asphenol alcohols, phenol aldehyde resins and the like, S- andN-containing epoxides (for example N,N-diglycidylaniline,N,N′-dimethyldiglycidyl-4,4-diaminodiphenylmethane) and also epoxidesprepared by customary methods from polyunsaturated carboxylic acids ormonounsaturated carboxylic esters of unsaturated alcohols, glycidylesters, polyglycidyl esters, which may be obtained by polymerization orcopolymerization of glycidyl esters of unsaturated acids or areobtainable from other acidic compounds (cyanuric acid, diglycidylsulfide, cyclic trimethylene trisulfone and/or derivatives thereof, andothers).

Very suitable ethers are, for example, 1,4-butanediol diglycidyl ether,polyglycerol-3 glycidyl ether, cyclohexanedimethanol diglycidyl ether,glycerol triglycidyl ether, neopentyl glycol diglycidyl ether,pentaerythritol tetraglycidyl ether, 1,6-hexanediol diglycidyl ether,polypropylene glycol diglycidyl ether, trimethylolpropane triglycidylether, bisphenol A diglycidyl ether and bisphenol F diglycidyl ether.

Particular preference is given to the use of a crosslinker-acceleratorsystem (“crosslinking system”) described for example in EP 1 978 069 A1,in order to gain more effective control over not only the processinglife and crosslinking kinetics but also the degree of crosslinking. Thecrosslinker-accelerator system comprises at least one substancecontaining epoxide groups, as crosslinker, and at least one substancewhich has an accelerating effect on crosslinking reactions by means ofepoxide-functional compounds at a temperature below the meltingtemperature of the polymer to be crosslinked, as accelerator.

Accelerators used are more preferably amines (to be interpreted formallyas substitution products of ammonia; in the formulae below, thesesubstituents are represented by “R” and encompass in particular alkyland/or aryl radicals and/or other organic radicals), more especiallypreferably those amines which enter into no reactions or only slightreactions with the building blocks of the polymers to be crosslinked.

Selectable in principle as accelerators are primary (NRH₂), secondary(NR₂H) and tertiary (NR₃) amines, and also of course those which havetwo or more primary and/or secondary and/or tertiary amine groups.Particularly preferred accelerators, however, are tertiary amines suchas, for example, triethylamine, triethylenediamine, benzyldimethylamine,dimethylaminomethylphenol, 2,4,6-tris(N,N-dimethylaminomethyl)phenol andN,N′-bis(3-(dimethylamino)propyl)urea. As accelerators it is alsopossible with advantage to use polyfunctional amines such as diamines,triamines and/or tetramines. Outstandingly suitable arediethylenetriamine, triethylenetetramine andtrimethylhexamethylenediamine, for example.

Used with preference as accelerators, furthermore, are amino alcohols.Particular preference is given to using secondary and/or tertiary aminoalcohols, where in the case of two or more amine functionalities permolecule, preferably at least one, and preferably all, of the aminefunctionalities are secondary and/or tertiary. As preferredamino-alcohol accelerators it is possible to employ triethanolamine,N,N-bis(2-hydroxypropyl)ethanolamine, N-methyldiethanolamine,N-ethyldiethanolamine, 2-aminocyclohexanol,bis(2-hydroxycyclohexyl)methylamine, 2-(diisopropylamino)ethanol,2-(dibutylamino)ethanol, N-butyldiethanolamine, N-butylethanolamine,2-[bis(2-hydroxyethyl)amino]-2-(hydroxymethyl)-1,3-propanediol,1-[bis(2-hydroxyethyl)amino]-2-propanol, triisopropanolamine,2-(dimethylamino)ethanol, 2-(diethylamino)ethanol,2-(2-dimethylaminoethoxy)ethanol, N,N,N′-trimethyl-N′-hydroxyethylbisaminoethyl ether, N,N,N′-trimethylaminoethylethanolamine and/orN,N,N′-trimethylaminopropyl-ethanolamine.

Other suitable accelerators are pyridine, imidazoles (such as, forexample, 2-methylimidazole) and 1,8-diazabicyclo[5.4.0]undec-7-ene.Cycloaliphatic polyamines as well may be used as accelerators. Suitablealso are phosphate-based accelerators such as phosphines and/orphosphonium compounds, such as triphenylphosphine ortetraphenylphosphonium tetraphenylborate, for example.

It is also possible that even a polymer foam that per se has theproperty of pressure-sensitive adhesiveness, with a polymer basisconsisting of polyacrylate(s), has been coated on its upper and/or lowerside with a PSA, with the polymer basis of this PSA preferably likewiseconsisting of polyacrylates. Alternatively it is possible to laminatedifferent and/or differently pretreated adhesive layers, in other words,for example, pressure-sensitive adhesive layers and/or heat-activatablelayers based on polymers other than poly(meth)acrylates, to form thefoamed layer. Suitable base polymers are natural rubbers, syntheticrubbers, acrylate block copolymers, vinyl aromatic block copolymers,especially styrene block copolymers, EVA, polyolefins, polyurethanes,polyvinyl ethers and silicones. These layers preferably contain nosignificant fractions of migratable constituents, whose compatibilitywith the material of the foamed layer is sufficiently good that theydiffuse in significant amount into the foamed layer and alter itsproperties.

Generally speaking, the soft phase of the adhesive tape may comprise atleast one tackifying resin. Tackifying resins which can be used are, inparticular, aliphatic, aromatic and/or alkylaromatic hydrocarbon resins,hydrocarbon resins based on pure monomers, hydrogenated hydrocarbonresins, functional hydrocarbon resins, and natural resins. Thetackifying resin is preferably selected from the group encompassingpinine resins, indene resins and rosins, their disportionated,hydrogenated, polymerized and/or esterified derivatives and salts,terpene resins and terpene-phenolic resins, and also C5, C9 and otherhydrocarbon resins. Combinations of these and further resins may also beused advantageously to adjust the properties of the resultant adhesivein line with requirements. More preferably the tackifying resin isselected from the group encompassing terpene-phenolic resins and rosinesters.

The soft phase of the adhesive tape may comprise one or more fillers.The filler or fillers may be present in one or in two or more layers ofthe soft phase.

Preferably the soft phase comprises a polymer foam, and the polymer foamcomprises partially or fully expanded microballoons, particularly if thepolymer basis of the polymer foam comprises one or more polyacrylates,and very preferably if the polymer basis of the polymer foam consists ofone or more polyacrylates. Microballoons are elastic hollow sphereswhich have a thermoplastic polymer shell; they are therefore alsoreferred to as expandable polymeric microspheres or as hollowmicrospheres. These spheres are filled with low-boiling liquids or withliquefied gas. Shell material used includes, in particular,polyacrylonitrile, polyvinyl dichloride (PVDC), polyvinylchloride (PVC),polyamides or polyacrylates. Low-boiling liquid more suitably includes,in particular, lower alkanes, such as isobutane or isopentane, which areenclosed as a liquefied gas under pressure in the polymer shell.Physical action on the microballoons, through exposure to heat, forexample, particularly by supply of heat or generation of heat, broughtabout for example by ultrasound or by microwave radiation, first causesthe outer polymer shell to soften, and at the same time the liquidblowing gas located within the shell undergoes transition into itsgaseous state. Given a certain pairing of pressure and temperature—alsoreferred to as the critical pairing—the microballoons undergoirreversible expansion, and expand three-dimensionally. Expansion is atan end when the internal pressure matches the external pressure. As thepolymeric shell is retained, the result is a closed-cell foam.

A large number of types of microballoons are available commercially,such as, for example, from Akzo Nobel the Expancel DU (dry unexpanded)products, which differ essentially in their size (6 to 45 μm diameter inthe unexpanded state) and in the starting temperature they require forexpansion (75° C. to 220° C.).

Also available are unexpanded microballoon products, in the form of anaqueous dispersion having a solids fraction or microballoon fraction ofaround 40 to 45 wt %; additionally, there are polymer-boundmicroballoons (masterbatches), for example in ethylene-vinyl acetatewith a microballoon concentration of around 65 wt %. Obtainable,furthermore, are what are called microballoon slurry systems, in whichthe microballoons take the form of an aqueous dispersion with a solidsfractions of 60 to 80 wt %. The microballoon dispersions, themicroballoon slurries and the masterbatches, like the DU products, aresuitable for foaming a polymer foam present in the soft phase of theadhesive tape.

With particular preference the polymer foam comprises microballoonswhich in the unexpanded state at 25° C. have a diameter of 3 μm to 40μm, more particularly of 5 μm to 20 μm, and/or which after expansionhave a diameter of 10 μm to 200 μm, more particularly of 15 μm to 90 μm.

The polymer foam contains preferably up to 30 wt % of microballoons,more particularly between 0.5 wt % and 10 wt %, based in each case onthe total mass of the polymer foam.

The polymer foam of the soft phase of the adhesive tape—to the extentthat this phase comprises a polymer foam—is preferably characterized bythe substantial absence of open-cell cavities. With particularpreference the proportion of cavities without their own polymer shell,i.e. the proportion of open-cell caverns, in the polymer foam is notmore than 2 vol %, more particularly not more than 0.5 vol %. Thepolymer foam is therefore preferably a closed-cell foam.

The soft phase of the adhesive tape may optionally also comprisepulverulent and/or granular fillers, dyes and pigments, including inparticular abrasive and reinforcing fillers such as, for example, chalks(CaCO3), titanium dioxides, zinc oxides and carbon blacks, and includingin high fractions, i.e. from 0.1 to 50 wt %, based on the total mass ofthe soft phase.

Further possible constituents of the soft phase may includelow-flammability fillers such as, for example, ammonium polyphosphate;electrically conductive fillers such as, for example, conductive carbonblack, carbon fibers and/or silver-coated beads; thermally conductivematerials such as, for example, boron nitride, aluminum oxide, siliconcarbide; ferromagnetic additives such as, for example, iron(III) oxides;other additives for increasing volume, such as, for example, expandants,solid glass beads, hollow glass beads, carbonized microbeads, hollowphenolic microbeads, microbeads made of other materials; silica,silicates, organically renewable raw materials such as, for example,wood flour, organic and/or inorganic nanoparticles, fibers; ageinginhibitors, light stabilizers, antiozonants and/or compounding agents.Ageing inhibitors that can be used are preferably not only primaryinhibitors, e.g. 4-methoxyphenol or Irganox® 1076, but also secondaryageing inhibitors, e.g. Irgafos® TNPP or Irgafos® 168 from BASF,optionally also in combination with one another. Other ageing inhibitorsthat can be used are phenothiazine (C-radical scavenger) and alsohydroquinone methyl ether in the presence of oxygen, and also oxygenitself.

The thickness of the soft phase is preferably 200 to 1800 μm, morepreferably 300 to 1500 μm, more particularly 400 to 1000 μm. Thethickness of the soft phase is determined according to ISO 1923.

The joining of hard phase and soft phase, or else of layers provided inthe hard and/or soft phase, to one another to form the adhesive tape maybe accomplished, for example, by laminating or coextrusion. It ispossible that hard phase and soft phase are joined to one anotherdirectly, in other words without mediation. It is equally possible thatone or more adhesion-promoting layers are disposed between hard phaseand soft phase. The adhesive tape, furthermore, may comprise furtherlayers.

Preferably at least one of the layers to be joined to one another, morepreferably a plurality of the layers to be joined to one another, andvery preferably all of the layers to be joined to one another, has orhave been pretreated by Corona (with air or nitrogen), plasma (air,nitrogen or other reactive gases or reactive compounds employable asaerosol) or flame pretreatment techniques.

Preferably all of the layers in the diecut have the same shape and sizeand are arranged congruently.

A typical size for the diecut, allowing many of the smaller holes to beclosed, is represented by a (circular) disk having a diameter of 10 to100 mm, more particularly 20 to 60 mm, especially 30 to 40 mm.

The method of the invention for closing a hole especially in a vehiclebody with a diecut of the invention simply involves applying the diecutto the hole to be closed, in such a way that the hole is completelycovered by the diecut.

It is preferred for the diecut to be applied concentrically over thehole to be closed.

The contours of the diecut advantageously correspond to the contour ofthe hole to be closed. In this way the overlap of the individual layersof the diecut is symmetrical. The margin of overlap is preferablybetween 3 and 20 mm, more preferably between 5 and 10 mm.

The diecut of the invention is superior to the solutions known from theprior art, particularly under heightened mechanical stress.

The diecut is distinguished by:

-   -   very high flame retardancy    -   very high load-bearing capacity/tear resistance/puncture        resistance    -   very good sealing with respect to moisture/moisture barrier    -   very good sealing with respect to noise/sound damping    -   repaintability    -   PVC adhesion

According to one advantageous embodiment of the invention, the diecuthas puncture resistances of 200 to 2000 N.

The surface of the diecut part is attractive and smooth in respect ofoptical and tactile qualities, and consequently has good repaintability.

Test Methods

The measurements are conducted (unless otherwise indicated) undertesting conditions of 23±1° C. and 50±5% relative humidity.

Molar Mass Mn and Weight-Average Molar Mass Mw, and Polydispersity PD

The figures for the number-average molar mass Mn and the weight-averagemolar mass Mw and also the polydispersity PD in this specificationrelate to the determination by gel permeation chromatography (GPC). Thedetermination is made on 100 μl of sample having undergone clarifyingfiltration (sample concentration 4 g/I). The eluent used istetrahydrofuran with 0.1 vol % of trifluoroacetic acid. The measurementis made at 25° C.

The precolumn used is a PSS-SDV-type column, 10 μm, 10³ Å, 8.0 mm*50 mm(statements here and below in the following order: type, particle size,porosity, internal diameter*length; 1 Å=10⁻¹⁰ m). Separation takes placeusing a combination of the columns of type PSS-SDV, 10 μm, 10³ Å andalso 10⁵ Å and 10⁷ Å each of 8.0 mm×300 mm (columns from PolymerStandards Service; detection by means of Shodex R171 differentialrefractometer). The flow rate is 1.0 ml per minute.

Calibration is carried out using the commercially available ReadyCal-Kitpoly(styrene) high from PSS Polymer Standards Service GmbH, Mainz. It isconverted using the Mark-Houwink parameters K and alpha universally intopolymethyl methacrylate (PMMA), and so the data are reported in PMMAmass equivalents.

K Value

The principle of the method is based on capillary-viscosimetricdetermination of the relative solution viscosity. For this purpose thetest substance is dissolved by shaking for thirty minutes in toluene, togive a 1% strength solution. In a Vogel-Ossag viscometer at 25° C. theflow time is measured and from this, in relation to the viscosity of thepure solvent, the relative viscosity of the sample solution isascertained. The K value can be read off from tables by the method ofFikentscher [P. E. Hinkamp, Polymer, 1967, 8, 381] (K=1000 k).

Glass Transition Temperature

The glass transition temperature is determined by means of dynamicscanning calorimetry (DSC). This is done by weighing out 5 mg of anuntreated polymer sample into an aluminum crucible (volume 25 μL) andclosing the crucible with a perforated lid. Measurement takes placeusing a DSC 204 F1 from Netzsch. For inertization, operation takes placeunder nitrogen. The sample is first cooled to −150° C., then heated to+150° C. at a heating rate of 10 K/min, and again cooled to −150° C. Thesubsequent, second heating curve is run again at 10 K/min, and thechange in the heat capacity is recorded. Glass transitions arerecognized as steps in the thermogram.

The glass transition temperature is evaluated as follows (see FIG. 2):

A tangent is applied in each case to the baseline of the thermogrambefore and after {circle around (2)} the step. In the region of thestep, a balancing line {circle around (5)} is placed parallel to theordinate in such a way that it intersects the two tangents, specificallyso as to form two areas {circle around (3)} and {circle around (4)} ofequal content (between in each case the tangent, the balancing line, andthe measuring plot). The point of intersection of the balancing linesthus positioned with the measuring plot gives the glass transitiontemperature.

Peel Adhesion

The peel adhesion (in accordance with AFERA 5001) is determined asfollows: the defined substrate used is galvanized steel sheet with athickness of 2 mm (obtained from Rocholl GmbH). The bondable sheetlikeelement under investigation is cut to a width of 20 mm and a length ofabout 25 cm, is provided with a handling section, and immediatelythereafter is pressed onto the selected substrate five times using a 4kg steel roller, with a rate of advance of 10 m/min. Immediately afterthat, the bondable sheetlike element is peeled from the substrate at anangle of 180° using a tensile testing instrument (from Zwick) with avelocity v=300 mm/min, and the force needed to achieve this at roomtemperature is recorded. The recorded value (in N/cm) is obtained as theaverage from three individual measurements.

Puncture Resistance

With the puncture resistance, a determination is made of the maximumloading force of a diecut bonded over a hole at the point of puncture(for example, for closure of holes in the automobile industry).

Using a circular diecut, a hole in a metal sheet is closed. Testingtakes place either immediately after bonding or after the prescribedstorage condition. The maximum force recorded is reported as thepuncture resistant result in N. The maximum force to puncture the testspecimen is ascertained using a tensile testing machine. This tensiletesting machine loads the bonded diecut part centrally with a die, whichmoves downward at 300 mm/min until a penetration depth of 20 mm has beenreached.

The method is based on the use of a tensile testing machine, which has aspike clamped into its upper force recorder, the spike being moved atconstant velocity (300 mm/min) toward a horizontally positioned hole ina metal sheet which is in turn closed with the diecut part. The holeselected is a circular cutout with a diameter of 30 mm. The steel sheetis 0.7 mm thick and is placed on a ring, allowing the spike to passthrough the hole to 20 mm when it presses the hole closure. The point ofthe spike is rounded and represents the head of an ISO 8677 cup squarebolt, having a diameter of 20 mm and an arc height of 3 mm, which hasbeen welded to a recorder. A measurement is made of the force requiredto press the spike 20 mm through the hole. Where metal-sheet adhesion isvery good, this value correlates to the tensile extension properties ofthe layerlike element in longitudinal and transverse directions.

The diecut under test (circular, 50 mm in diameter) is placed as far aspossible centrally and without air inclusions over the hole of the metalsheet and rolled down using a 4 kg steel roller (five times back andforth at 10 m/min over the entire width of the diecut). Testing takesplace, unless otherwise indicated, after less than 10 minutes frombonding (instantaneous testing). The test can be carried out both on thecarrier side and on the adhesive side. Unless otherwise indicated, it iscarried out on the carrier side, meaning that the carrier side of thediecut faces upward.

The test specimen is placed and secured on the specimen holder in such away that the diecut lies centrally on the holder and centrally beneaththe die. The machine is then started with a velocity of 300 mm/min andthe diecut is pressed downward through the hole in the metal sheet. Thetest ends when a penetration depth of 20 mm has been reached, even ifthe test specimen here has only been pressed in, and not yet punctured.

The puncture resistance is the average value from three individualresults.

If the diecut has not been punctured, or if the bond has come undone,the result is reported preceded by “greater than/equal to”.

Fire Tests

A diecut part (10) having a diecut-part diameter of 50 mm is appliedconcentrically to a cathodically electrocoated metal sheet (20)containing a circular hole with a hole diameter of 30 mm.

The diecut part is pretreated beforehand in an oven at 160° C. for 30min.

The diecut is then allowed to cool to room temperature. This waitingtime embraces a timespan of at least two hours.

Using a Bunsen burner (40), a flame is applied to the outer surface ofthe diecut part, to produce a temperature of 1000° C. +/−100° C. at theK-type temperature sensor (30) directly and centrally in front of thediecut.

There is a vertical test (specimen vertical, flame horizontal) and ahorizontal test (specimen horizontal, flame vertical).

FIG. 3a shows the vertical test, and FIG. 3b the horizontal test.

Below, on the basis of a figure, the diecut for the permanent closing ofholes especially in metal sheets or in plastics parts of automobilebodies is to be elucidated in more detail, without any intention of arestrictive effect in any form.

-   FIG. 1 shows a hole in a body that is to be closed, and also the    state after closure of the hole that was to be closed.

The body 20 contains, as a result of its construction, a hole 50 whichis to be closed.

For this purpose, a diecut 10 with a carrier having the followingconstruction

1 aluminum foil 12 PU adhesive 2 laid glass fabric 3 water-basedacrylate composition 4 PU foam, flame-retardant

-   -   5 foamed acrylate adhesive        is secured on the hole 50 in such a way that the hole 50 is        completely covered by the diecut 10.

The area of the diecut 10 is greater than the area of the hole 50 to beclosed, and so the hole 50 is closed over its full area.

In the text below, the invention is elucidated in more detail by anexample, without wishing thereby to restrict the invention.

Inventive Example

Layer 1: aluminum foil 18 μm Layer 12: PU adhesive 7 g/m² Layer 2: laidglass fabric 85 g/m² Layer 3: water-based acrylate 95 g/m² compositionLayer 4: PU foam, 1.5 mm flame-retardant (from Unipoly) Layer 5: foamedacrylate 800 μm adhesive

Comparative Example

In the comparative examples, the layer 4, the PU foam layer, and alsothe optional layers 1, 12, 2 and 3 are replaced by the respective layerlisted in the table, and are likewise subjected to the vertical firetest (temperatures of 1000° C., up to a duration of at least 10 min).

It is found here that no layer produces a diecut which passes the firetest with comparably good results. The failure here is defined in thebreakthrough of the flame through the hole.

Thickness/ Supplier/ BW* of product carrier Material name material ProContra Time to failure Aluminum-laid tesa SE 1060 μm nonflammable lowtemperature 21 seconds glass fabric tesa ® 54332 resistance of 500° C.assembly in adhesive tape form Polyimide film with tesa SE 65 μm lowflammability low temperature 68 seconds silicone adhesive tesa ® 51408resistance of 300° C. (Melting) Aluminum tesa SE 80 μm nonflammable heatconduction, 17 seconds adhesive tesa ® 50575 adhesive melts tape Film oftesa SE 100 g/m² — readily flammable 17 seconds polyurethane acrylatePET film, Coveme 125 μm — heat conduction, PET 16 seconds aluminized andadhesive melt Laid glass fabric Mica Tapes 60 μm (1) nonflammable, nolonger insulating 21 seconds (1) coated with Europe 80 μm (2) very highat high temperatures, 27 seconds (2) phyllosilicates 100 μm (3)temperature melting of the adhesive 32 seconds (3) (phlogopite) 110 μm(4) resistance of 29 seconds (4) around 1000° C., effective insulationat lower temperatures Woven glass Jiangsu Jiuding 180 μm nonflammable,heat conduction, melting 131 seconds fabric, thin New Material Coflexible of the adhesive, fraying Ltd./ at the edges, low EP 200Yadhesion by the adhesive Woven glass Jiangsu Jiuding 110 μm nonflammableflame passes through 25 seconds fabric, New Material Co the openings inthe open porosity Ltd. fabric, fraying at the JD 512FR edges, adhesionof the adhesive is low Aramid fibers and Frenzelit/ 1000 μm effectiveinsulation designed for the HT 123 seconds functional active Novaform2500 at lower range, yet (low) ingredient temperatures, flammabilitycombination joined basis weight by nitrile-butadiene binder HT papersDBW 2000 μm nonflammable, dusts, open porosity, 60 seconds (SiO₂, CaO,HT Papier 607 very high low adhesion of the MgO) high temperatureadhesive resistance of around 1000° C., effective insulation Silicatewool DBW 4000 μm nonflammable, dusts (possibly 300 seconds (SiO₂, Al₂O₃)powermat ® S very effective carcinogenic), insulation fraying, difficultto handle, low adhesion of the adhesive Woven silicate Fingerhuth/ 800μm (1) nonflammable fraying at the edges, 142 seconds (1) fabricsilTEX ® 1500 μm (2) low adhesion of the 235 seconds (2) 1608.VC2.LD (1)adhesive, partly open silTEX ® porosity 1615.HTLE.T (2) Woven glassJiangsu Jiuding 400 μm nonflammable, fraying at the edges, not subjectedto this test, fabric, thick New Material Co effective low adhesion ofthe owing to the poor Ltd. insulation adhesive adhesion propertiesBWT600-83 relative to the adhesive Aerogel mats Stadur 2500 μmnonflammable stiff, dusty, unstable not subjected to this test, Pyrogel2250 adhesion of the owing to the poor adhesive adhesion propertiesrelative to the adhesive Woven Fingerhuth 3000 μm — low temperature notsubjected to the test, para-aramid resistance of 350° C. owing to thelow fabric (Kevlar) temperature resistance Five-layer Unipoly 1500 μmnonflammable, NO failure in the ≥10 min construction FV-32 1.5T lieslike a protective fire test with PU foam cover over the (accordingadhesive, effective to the invention) heat insulation *: BW: basisweight

The advantages of the diecut of the invention over the prior art are asfollows:

-   -   fire resistance up to temperatures of 1000° C. and up to a        duration of at least 10 min    -   in both fire tests    -   low-temperature impact resistance    -   clean bonding and no oozing of adhesive    -   sufficient adhesion of the flame-retardant foam layer to the        acrylate-based pressure-sensitive adhesive (in contrast to        numerous comparison products, no cohesive fracture between the        layers).

What is claimed is:
 1. A diecut especially adapted for the permanentclosing of holes in metal sheets or in plastics parts, having a carriercomposed of an assembly, more particularly laminate in the specifiedlayer sequence, of optionally at least one first layer, which is formedby a metallic layer having a thickness of 10 to 40 μm, optionally atleast one second layer, which is formed by a woven glass fabric or laidglass fabric having a basis weight of 30 to 200 g/m², optionally atleast one third layer, which is formed by a first pressure-sensitiveadhesive having a basis weight of 70 to 200 g/m², at least one fourthlayer, which is formed by a flame-retardant foam having a thickness ofat least 0.5 to 2.5 mm, and at least one fifth layer, which is formed bya second, acrylate-based pressure-sensitive adhesive having a basisweight of 300 to 1800 g/m², and/or a thickness of 400 to 1800 μm,preferably 800 to 1500 μm.
 2. The diecut of claim 1, wherein the diecutincludes a first metallic layer having a thickness of 12 to 20 μm. 3.The diecut of claim 1, wherein the diecut incudes a first metallic layerwhich is a rolled metal foil.
 4. The diecut of claim 2, wherein thediecut includes a second layer of woven glass fabric or laid glassfabric having a basis weight of between 60 and 120 g/m².
 5. The diecutof claim 4 the warp thread count and/or the weft thread count for thesecond layer of woven glass fabric or laid glass fabric is 20 to 40/cm.6. The diecut of claim 1 wherein the diecut includes both a firstmetallic layer and a second layer in the form of a woven or laid glassfabric, having therebetween a further adhesive layer in the form of alaminating adhesive.
 7. The diecut of claim 1, wherein the diecutincludes a third layer, which is formed by a first pressure-sensitiveadhesive having a basis weight of 70 to 200 g/m², is a water-basedadhesive based on acrylate.
 8. The diecut of claim 1 wherein the fourthlayer, which is formed by a flame-retardant foam having a thickness of0.5 to 2.5 mm, is a layer of a polyurethane polymer foam which comprisesa flame retardant in a fraction of at least 1 wt % of flame retardantand less than 10 wt % of flame retardant.
 9. The diecut of claim 1wherein the fifth layer, which is formed by a second pressure-sensitiveadhesive having a basis weight of 300 to 1800 g/m², is a foamed,acrylate-based adhesive.
 10. A method of permanently closing a hole in ametal sheet or a plastic part, the method comprising the step ofapplying the diecut of claim 1 concentrically over the hole to beclosed.
 11. The diecut of claim 1, wherein the diecut comprises contourswhich correspond to the contour of a hole to be closed therewith and thediscut includes a margin of overlap of between 1 and 20 mm.
 12. A holein a vehicle body closed with a diecut of claim 1.